This article would discuss the factors affecing the results of animal experimentation in three ways.Experimental animals are the acted objects, and the final expressed main body of outside combinations. And outside combinations act through animal metabolism.The difference of animal race and individual influences the metabolism of outside combination in the animal bodies and, therefore, the action of outside combinations.The environmental factors not only affect the states of experimental animals, but also act on outside combinations.The path and the way through which outside combinations enter the animal bodies influence the metabolism and expression of outside combinations in body.