Considering consumer's preference for poverty alleviation, this paper studies the three-level agricultural products supply chain consisting of single farmer cooperatives, single agricultural product processors and single e-commerce platforms. It is found by the study that when the e-commerce platform and cooperative don't encourage the processor, the processor would not participate in poverty alleviation. And when the yield is at a high level, it is possible for enterprises to increase their profits through participation in poverty alleviation, and there is an optimum level of poverty alleviation to maximize profits. Finally, through the design of a two-part contract of "farmer security deposit $+$ e-commerce platform subsidy", processors are stimulated to actively participate in poverty alleviation so that the supply chain can achieve Pareto improvement.This study provides theoretical support for the actual establishment of cooperative mechanisms for enterprises to help farmers increase their profits while improving their own profits.