By analyzing a nationally representative survey data，this paper responds to the classic proposition of the relationship between family intergenerational cooperation and family utility，focusing on the influence of intergenerational investment on the intergenerational economic support of the rural elderly in China．Using logistic multivariate model and propensity score matching method，we have found that parent income and number of offspring affect the relationship between offspring investment and rural elderly intergenerational economic support．In the three-generation intergenerational exchange，the investment on the grandchild generation has a significantly positive impact on the intergenerational economic support of the rural elderly．In the three-generation inter-generational cooperation，the investment on the third generation has a positive impact on family utility．In the context of the positive relationship between intergenerational cooperation and utility of rural elderly family，fertility preferences become an important parameter affecting family utility，being aware of the imbalance of intergenerational exchange and the growth of the child-generation family utility．