The Pacific oyster Crossostrea gigas and the Portuguese oyster C. angulata are two subspecies and are also the most important two cultured oysters in China, which have been separately cultured in North and South China. In order to improve production by exploring heterosis, two hybrid groups of NS (N♂?S♀) and SN (S♂?N♀) and two purebred groups of NN (N♂?N♀)and SS (S♂?S♀) were established using a diallel cross design with the parents of the Pacific oyster from Qingdao of Shandong (N) and the Portuguese oyster from Shantou of Guangdong (S). The present results showed that hybridization between the two close related species was successful. Two production traits of growth rate and survival rate for hybrids were both improved, and significant heterosis for them was obtained. The hybrids grew faster than the purebreds, and heterosis for growth rate is 37.44℅ at larvae stage and 42.47℅ at spat stage, respectively. The hybrids also survived more that the purebreds, and heterosis for survival rate is 76.80% and 107.70% for larvae on day 8 and 14, and 17.30%, 15.62% and 9.08%, respectively. Our study showed that some problems such as harder breeding seeds, lower survival rate, slower growth, and smaller size influencing oyster production could be solved by cross breeding between the two subspecies.