Abstract： Objective To optimize the extraction process of fatty oil from Cassiae obtusifolia L.Methods A method of orthogonal test was developed with the index of the relative content of fatty oil ( ml/100 g).The factors of grinding degree,extraction time,soak time and solid-liquid ratio were investigated to optimize the extraction efficiency process of fatty oil from Cassiae obtusifolia L.Results The effect on the efficiency of extraction was affected by grinding degree,extraction time,soak time and solid-liquid ratio(R = 16.53,0.31,2.48,1.97,respectively).The factors of grinding degree( F = 105.8592,P ＜ 0.01 ) and extraction time( F = 27.4856,P ＜ 0.05 ) had statistical significance in the analysis of variance.Conclusion Best extracting process:take powder through 10 mesh sieve,dipped in cold solution for 12 hours,then heat reflux extract for two times,take the leaching when in 30min and 2 hours.The solid-to-liquid ratio is 1/6.