Abstract: In this paper, the concept and the expression of the partial distribution and the partial process are put forward. Bv them, the variations of commodity price can be described, analyzed, and researched. The relations of the cost price, the market price, the risk of cost price and the risk of market price of commodity are advanced in analytic expressions, which can be applied to pricing and to measuring the risks of the spots, the securities, the futures and the options in market. The Security Indexes are designed in analytic expressions. So we can use them to measure and evaluate the development security and investment security in the society, the economy, the finance, and so on.

Key words: partial distribution, pricing model, logical price, the Security Index