Goods contracts have the characteristics of standardization, and trading in fixed places is a substitute for the quantity, quality grade and delivery grade of their subject matter. Futures contracts traded in the futures market are standardized in the quantity, quality grade, delivery grade, premium standard of substitutes, delivery place and delivery month, which makes futures contracts universal. According to the relevant public information, only the futures price is the only variable in the futures contract, which is generated by the open bidding of the exchange. The futures contract of each commodity stipulates the unified and standardized quantity and quantity unit in terms of terms, editing and broadcasting, quantity and unit terms and contract forms, which are collectively called trading units.