To dertimine the optimal microalgae diet for massive clam culture, this experiment was conducted to investigate the effects of different microalgae diets (Cyclotella sp., Chlorella sp., Scenedesmus dimorphus, monosporidium contortum, and mixed four microalgae) on the growth, pearl producing function, nutrition composition and shell nacre color of Hyriopsis cumingii, using a single factor experiment method. The results showed that the growth of the clam was significantly different with different microalgae diets. The growth rate of weight, shell length, shell width and shell height of Hyriopsis cumingii was the highest when fed by Cyclotella sp., Scenedesmus dimorphus came second, with its growth rate of shell length slightly higher than Cyclotella sp., but no significantly difference (P>0.05). The growths of the mussel for the groups of Chlorella sp., Monoraphidium contortum and mixed algae group were poor. The highest production gain of pearl was 16.23%±1.23% when fed by Cyclotella sp., significantly higher than other four groups (P<0.05). The perfect round pearls rate in Cyclotella sp. and Scenedesmus dimorphus groups was significantly higher than in Monoraphidium contortum group (P<0.05). The trace element content of the foot and mantle was significantly affected by diet (P < 0.05). The highest Ca content of foot was observed in mussels fed Cyclotella sp. (12637.3±624.39 mg/kg), It is significant effect on shell nacre color (P<0.05). Lowest brightness of shell nacre color came with Cyclotella sp., together with smallest chromatic aberration, and higher saturation. For the mixed algae group, the highest brightness of shell nacre color and chromatic aberration, and the lowest saturation were found (P<0.05). The brightness, chromatic aberration and saturation of the Scenedesmus dimorphus group were all at intermediate levels. In conclusion, Cyclotella sp. may be the best diet choice for intensive Hyriopsis cumingii, and followed by Scenedesmus dimorphus.