The invention discloses a grain-rapeseed double-harvesting planting method for a red-soil rice field. The method comprises the steps: (1) selecting a middle-season rice and ratoon rice variety, planting middle-season rice in a red-soil region in a rice seedling transplanting or throwing manner at the first ten days of May, and reaping the middle-season rice at the last ten days of August; and carrying out stubble-remaining regrowing so as to obtain ratoon rice, strengthening field management, and reaping the ratoon rice at the last ten days of October; and (2) selecting a hybridized double-low rape variety, and carrying out interplanting 5 to 7 days before reaping the ratoon rice at the last ten days of October; and carrying out mechanical harvesting and threshing when rape pods of an entire rape field are yellow and seed coats are black brown from the end of April to the beginning of May in an ensuing year. According to the method, on one hand, high and stable yielding of rice and rape can be simultaneously guaranteed from planting time; meanwhile, the middle-season rice is planted in advance by 20 to 30 days (the first or middle ten days of May) in this research, so that the condition that the ratoon rice is reaped at the end of October is ensured, thus, sufficient planting time for rape planting is set aside, and the planting of the middle-season rice is not affected after the rape is reaped; and bumper harvest in both grains and rapeseed is expected.