P1, P2, F1, F2, B1, B2 in five combinations were used as materials and the genetic variability of grain protein content were analyzed. The results show protein content in rice grain belongs to quantitative traits controlled by polygene, F1 and backcross generations present approximately normal distribution in continuous variation. There are some plants whose protein content of grain are higher than parents with high content among segregating generations. Selection was undertaken beginning with low generations, it is probable to obtain fine individuals. Parents' protein content affects progenies, whereas the female parents have much bigger effect. It is beneficial to use parents with high protein content as female parents in breeding combinations.