Abstract: This study used Castor cuhivar Lm-aLmAB2 as object for research inflorescence differentiation of its three types progeny in microscopic level and confirmed the critical transitional period from vegetative growth to reproductive growth. We also provided a reference for ectopically cultivation and breeding of castor in northeast region. The results were as follows： the climacteric of flower bud differentiations in different types were about 5 to 6-leaf stage; castor inflorescence was panicle,the tight arrangement of floret followed by bisexual line, isofemale line,female line;the diameter of inflorescence in bisexual line was largest than isofemale line and female line;flower was incomplete;the specificity salix-shaped leaf occurred at 7-leaf.