The regulation of the two parties of a relational contract becomes one of the effective governance modes because the new classical contract is restricted by the difficulties of governance of the third party while the governance of the contract needs such governance measures as reciprocity and trust and so on. We suppose that the enterprise can observe the outcome of farmer’s behavior and conjecture the motive or belief of farmer’s behavior, this paper constructs reciprocal and trust contract between leading enterprise and farmers and analyzes the optimal strategy of both parties on the basis of the construction of comparison relation between choice sets. The result shows that if the increasing of farmer’s effort leads to the increasing of optimal return in the choice set of an enterprise or the decreasing of minimum return level in choice set of rural households, the enterprise’s optimal response is to increase the proportion shared by rural households in total earnings, for example, raising the rank of agricultural products, if this point can be forecasted, the optimal strategy of agricultural households should be trying to boost effort level, thus, through reciprocal behaviors between leading enterprises and rural households, the trust degree between the two parties can be enhanced so that transaction stability can be strengthened.