The primary infection sources and main influencing factors of fusarium wilt of castor were studied in this experiment.The results showed that disease-producing germ in the soil,dis ease plants or tissues,disease -producing germ in the seeds and disease -producing germ in the organic manure are the main primary infection sources of fusarium wilt of castor.Fusarinm wilt of castor was influenced by the following factors,the rotation of crops,the different growth period,soil moisture and air humidity,varieties and fore-crop.