Abstract: In order to understand the influence of rural floating population on the agricultural economy and maintain the regional food security, this paper took Shanghai as an example for study based on the total output value in respect of farming, forestry, animal husbandry and fishery industries and rural floating population data from 1992 to 2012 in Shanghai. It analyzed the relationship between the rural floating population and planting, forestry, animal farming and fishery industries, and the contribution degree of rural floating population on farming, forestry, animal farming and fishery industries by using grey correlation and the modified Douglas production function. The results showed that the correlation between the rural floating population and 4 related industries are very high, and the contribution value to the farming industry and animal husbandry is quite positive, the contribution value to the forestry and fishery industry is negative. On this basis, this paper also made some suggestions to guide the rural floating population to the farming industry and animal husbandry, which would be very conducive to the development of agricultural economy.