Based on the transaction characteristics between the meatpacking enterprise and farmer in the food supply chain and the incomplete contract theory, the paper constitutes the shortterm cooperate transaction contraction model with the hypothesis that the both parties promise not to renegotiate. The conclusions show that the status of enterprises as test-agents is crucial to ensure the farmer to declare his type honestly in order to guarantee the special investment of both the parties optimized, and the limitation of the sub-game refined Nash equilibrium is that the payment function of enterprise must be a monotonous one so that the enterprise can tell the truth.