Formation of Customs
China is known as "the State of Ceremonies". There are a number of social and moral norms to follow in people's living, production, social activities etc. These norms need to be revealed by certain etiquettes and formalities. Ancient people bear doubts on astronomy, geography, sun and moon rotation, natural hazards and decease, so they always have fears to the nature and thus generate a kind of ignorant worshipping. As time goes, recognized customs and rites are formed, some of which still influence people today.

Through marriage rites, the marriage system of humans is regulated and the happening of incest avoided. Ancient China has experienced Communal Marriage, Concubine Marriage, Inter-clan Marriage, and Dual Marriage.

Communal Marriage means in the ancient times, people were not restricted by emotion. They only made relationship for physiological needs. The father and daughter could even have sexual intercourse. This will easily generate disabled child. It is totally an immoral behaviour.

Concubine Marriage is restricted by age groups. Marriage between parents and their children was prohibited, but marriage between brothers and sisters still prevailed.

Inter-clan marriage excludes marriage between brothers and sisters, but brothers and sisters with different surnames can still get married. This reveals that people's moral concept to marriage gradually improved. As such, the chance of incest is greatly reduced.

Dual Marriage is the practice of one husband and one wife, and was prevalent in thriving times.

Today monogamy is practised.

Three Letters and Six Etiquette
Marriage in Chinese culture is considered the joining of two families. It is such an important matter that various marriage rituals (some may even be very complicated) have been developed. They were closely observed. For instance, people need a middle-man's help for getting married. Etiquettes and Ceremonials (Yili) is a book about stipulated marriage process in China. "Three Letters and Six Etiquette" are the most important and essential processes in marriage ceremonials. They are elaborated in detail as follows.

Three Letters
Request Letter: This letter confirms the formal arrangement of a marriage. It is sent by the groom's family to the bride's family. This letter is normally presented with the initial gifts for the bride's family.
Gift Letter: This letter accompanies the formal gifts for the bride's family. It is actually a gift list that records the description and quantity of the gifts.
Wedding Letter: This letter is presented to the bride's family on the day of the wedding. It confirms the act of bringing the bride into the groom's family.

Six Etiquette
Request for Marrying the Bride: Match-making is the most important thing in a marriage. After the groom's family has spotted a young girl whom the groom wants to marry, the family will hire a spokeswoman to communicate their wish to the potential bride's family. If both parties agree, they will be mutually selected as their spouse

Request for Bride and Groom's Birth Dates: After the match-making process, the groom's family will request for the bride's Eight Letters through the spokeswoman. That is the bride's name and birthday. After obtaining the Eight Letters of the groom and potential bride, a fortune-telling master will be hired to determine whether the two match each other.

Initial Gifts for the Bride's Family: If the potential bride's birthday is acceptable, the groom's family will request the spokeswoman to send some initial gifts accompanied by the gift letter.

Formal Gifts for the Bride's Family: The groom's family will pick a "good day" and send the bride's family the following bridal gifts: gifts, cash, cakes and food and sacrifices for worshiping the ancestors. The gifts are for engagement. Therefore, this act confirms the marriage agreement between the two families.

Select the Wedding Date: The fortune telling master, hired by the groom's family, will select a "good day" according to the bride and groom's and their family's birthdays.

Wedding Day: The groom will go to pick up the bride.

It is not popular and necessary to complete the whole procedure of Three Letters and Six Etiquette in the 21st century. It has been largely simplified, only the important ones are kept today.