Abstract: Developing the indica compatible japonica lines (ICJLs) in rice may be an important procedure of overcoming the hybrid sterity to utilize the heterosis of F 1 hybrids between indica and japonica for raising rice grain yield. The heterosis of F 1 hybrids between the candidate ICJLs and indica varieties (lines) was identified. The results were as follows: 1.The F 1 hybrids between ICJL G3005 4 1 and indica varieties (lines) had great mid parent heterosis in the theoretic grain yield but the other indica compatible weak japonica lines and indica varieties (lines) had little mid parent heterosis. 2.The F 1 hybrids with great mid parent heterosis in the theoretic grain yield between ICJL G3005 4 1 and indica varieties (lines) had the great total grains and the great filled grains per panicle, normal seed set rate and proper growth duration and proper plant height. 3.The mid parent heterosis of F 1 hybrids in the theoretic grain yield was not correlated to parent average and the parent similitude coefficient identified by SSR(simple sequence repeat) markers at significant level.