The Bio_mass and the development of root system of different rice varieties cultivated under the condition of applying pure organic fertilizer without herbicide and chemical fertilizer were studied.The result indicated:①The number of secondary roots increased 103 averagely at different soil layer under pollution free condition compared with conventional cultivating condition,but the root length was 3 cm shorted.②The root number showed positive correlation with grain weight per hill and Biomass.③The content of amylose under pollution free condition was higher than that under conventional cultivation condition,the content of protein have n't obvious change.④The average yield increased 5% under pollution free cultivation condition.