Thirty-six combinations were obtained using 6 photo-thermo-sterilities as female parentages and 6 restoring lines as male parentages to investigate the combining ability of head rice percentage in two-line hybrid rice. correlation analysis showed that head rice percentage of hybrids (F1) was significantly positively correlated to that of the male (restoring lines) and female (restoring lines) parentages, with correlation coefficient being 0.233 2 and 0.264 1 respectively. Analysis of combing ability for hybrids obtained by 6×6 incomplete diallel cross method showed that the difference of head rice percentage among F1 combinations was significant; the difference between general combining ability (GCA) in parentages and special combining ability (SCA) in combinations was significant in regard to head rice percentage. GCA in parentages played a greater role compared to the SCA in combinations. The variance of GCA occupied 65% of the whole genotype variance and that of SCA occupied 35%. And male parentages (genotype variance was 63.70) contributed more to GCA compared to the female parentages (genotype variance was 55.34).