Abstract: Pigment spot of castor（Phytophoya arasitica Dast）is a important disease,It's caused by Phytophthora,Serious harm period is from July to August.This disease became popular when temperature at 10 ~ 25 ℃ and air relative humidity above 85%.It is often lead to sotto, stem rot, fruit rot and leaf spot, abd etc,Then it is affect plant growth and yield of Castor.The precaution of the disease should be taken agricultural measure combine with pesticide.