The Yi people’s trading activity has gradually formed into a series of commodity trading "customary law" from their life; these rules have gone from accidental barter to the development process of trade fairs, rallies. The trade in commodity in Yi District can be divided into three types: aid exchange, access exchange and communication exchange. The applicable situation and the corresponding rules have their own characteristics. In the Yi and Han nationalities, the system of "provoking" and "insurance" are the most distinctive. The opium trade in modern times is the largest and most typical commodity trade of the Yi slave society. Although it has expanded the scale of commodity exchange, and has stimulated the economic development. However, it led to the social distortion in the Yi area.