Abstract: Rice substrate water holding capacity of different organic materials and its effect on seedling quality were studied through rice seedling pot experiment. In this paper,‘Longdao 11’was taken as the test material, and straw and rice husk as organic materials which were mixed with organic manure, peat, zeolite, vermiculite, fine sand, carbon powder, etc. by different proportions, and rice seedlings organic materials substrate tests were conducted. Results showed that, the density of organic materials seedling substrate and water holding capacity had a significant negative correlation, and water loss rate of different seedling organic materials substrates could meet rice seedling requirements within a certain range. CO₁C was the optimal substrate, at which no pests occurred during rice seedling cultivation, and the seedling quality was the best and good seedling effect was obtained. The use of organic materials substrate could meet requirements of rice seedlings transplanting, and would be applied to rice seedling production and had a good effect, which could replace soil of ordinary rice seedling.