Abstract: Taking both of the healthy plants of Pinus armandii and the plants infested by Cronartium ribicola as experiment materials, Fuchsine acid staining method was chosen from two different staining ways for sampled cut sections of the tissues of either healthy and infected Pinus armandii by microscopic examination, and then the Fuchsine acid staining method was testified through orthogonal test.The distribution of Cronartium ribicola pathogen inside the stem of infected Pinus armandii was determined, which would be helpful to the quarantine and control of Cronartium ribicola by providing the grass-root foresters with theoretical foundation.