This paper studied the influence of rice culture on family size. Rice planting and the suitability of rice planting have significant positive effect on family size. Using the rice/grain yield ratio and rice/grain planting area ratio to replace the rice planting, the conclusion is still robust. Using the reservoir density as the instrumental variable of rice planting, the influence is still significant. Rice planting leads to stronger collectivism culture, higher childbearing willingness, son preference, lower divorce rate and less family division tendency, resulting larger family size. Therefore, the fertility-incentive policy may be more effective in rice planting areas.