Abstract: The single ＂Tongbi5＂ castor seed was the study object in this paper.Aiming for optimizing extraction pro-cess of crude protein,a variety of methods of which BCA kit,UVwin5 ultraviolet software（v5.1.0） and Band Scan protein quantitative analysis software were used.The results were as follows,in the optimized extraction process of crude protein of a castor seed,the amount of buffer A is 3m L/g,time of precipitation with ammonium sulfate（70% satu-ration） is 12 h,and the amount of buffer A to dissolve precipitation is 3m L.It was found by measurement that the average quality of a castor seed is 0.2415 g,the average content of crude protein is 10.8908 mg.Ricin makes up crude protein by 37.79 and content of ricin is 4.1154 mg on average in a castor seed.