Abstract: The preparation process of organic fertilizer by solid-state fermentation of leaves residual of Eucommia ulmoides Oliv. was studied. Effects of four main factors, including bacteria combination, ratio of liquor to material, additive amount of glucose and fermentation time on the mass fraction of humic acid, were analyzed by using single factor method. Based on the single factor test, the process conditions of solid-state fermentation of Eucommia unmolds Oliv. were optimized by the orthogonal experiments method, and toxicity of the vested organic fertilizer was tested. The results showed that the optimum condition were the ratio of liquor to material 2.0:1, additive amount of glucose 1.5%, and inoculating the composite bacteria of white rot fungus and Trichoderma koningii to the Eucommia ulmoides Oliv., and fermentation time 6 days. In this experimental condition, the mass fraction of humic acid in the leaves residual of Eucommia ulmoides Oliv. could reach 38.31%. The results of toxicity test showed that the germination rate of brassica chinensis were all higher than 90%. It proved that the organic fertilizer prepared by leaves residual of Eucommia ulmoides Oliv. was nontoxic.