The anatomy of entophyte system of Arceuthobium sichuanense was observed with paraffin sectioning and light microscope.The endophytic system consisted of cortical strands within the bark and sinkers embedded in the xylem.The cortical strands extended by squeezing the cortex cells of host.When penetrating the periderm of host,the cortical strands developed aerial shoots;when contacting with and near to the secondary phloem of host,the cortical strands developed sinkers.Then,the sinkers penetrated the phloem and cambium of host,extended to the xylem and grew along with the xylem rays of host.The periderm of host became thickened when the penetration pegs and the cortical strands penetrated it.The number of host cortex cells increased where localized infection of A.sichuanense occurred.The results indicated that A.sichuanense can develop systemic infection and reflected the interaction between A.sichuanense and host at histopathological level.