Qingtian rice-fish coculture system is one of the first pilot sites of Global Important Agriculture Heritage System (GIAHS) designated by FAO in 2005. The optimization of rice-fish coculture mode such as the selection of optimal rice density in the coculture system will be much helpful to the local promotion of this rice fish coculture model. In this study, 3 rice planting density (by different line and plant spacing) were chosen in order to compare the effects of the rice spacing on the rice growth and yield, the survival rate (SR) and specific growth rate (SGR) of the fish (Cyprinus carpio var. color). The 3 rice cultivation densities (high, medium and low density) were plant spacings of 20 cm×30 cm, 30 cm×30 cm and 40 cm×30 cm, respectively. The results showed that:the tiller number and biomass of rice at low density (40 cm×30 cm) were significantly higher than those of the high density groups after elongation stage; there were obvious advantages of the rice stem characters at low density (40 cm×30 cm) among the 3 densities; and the cultivation density had no significant effect on rice yield. The grey correlation analysis showed that the greatest correlation with rice yield was the panicle length among the rice stem characters, and the greatest correlation with rice yield was the 1000-grain weight among rice yield compositions. The SGR of fish reached the highest value 4.54%±0.03% at the medium density (30 cm×30 cm), which was extremely significantly higher than that at the high density (20 cm×30 cm) 3.62%±0.04%. The survival rate of fish was not significantly different among treatments. Based on rice growth and production efficiency, the medium-density (30 cm×30 cm) of Qingtian rice-fish coculture system can be the priority to be used to get faster growth rates of fish while ensuring rice yield.