Farmers are linked with market by commodity contract, modern finance system is a feasible way for pushing the commodity contract, the efficiency and scope of the agricultural commodity contract pattern is restricted by the development of the agricultural finance structure.

Contraposing the viewpoint that commodity contract is superior to factor contract, this paper makes some researches ulteriorly into the stability of commodity contract.

A collaborative contract model with quantity flexibility is thus developed to stimulate both parties,with an optimum decision provided for the retailer to determine the upper limit of ordering quantity or orderin.