Abstract: Seven pine species were inoculated by pine wood nematode (PWN) Bursaphelenchus xylophilus at Nanjing, in next year the samples were taken above the inoculate sites of alive pines which did not have any outer symptom and isolated nematodes. The result showed that the latent infection of PWN was more common. and it varied on different pine species. After inoculation the susceptible pines, Pinus thunbergii and P. densiflora, died fast. When the inoculum dose was very small, the latent infection could happen. For resistant pines, P. taeda and P. elliiottii, the latent infection was more common and the PWN number in the samples was higher. For moderate resistant pines, P. rigida and P. massoniana, the universal level of latent infection and PWN number in the samples were mid. After inoculation P. echinata did not wilt and there were no any nematodes in the samples. The result of PWN transmission by Monochamus alternatus test showed that after maturition feeding of PWN free beetles on the pine branches inoculated by PWN, the beetles can carry PWN and transmit the nematodes to healthy pine branches.