Bursaphelenchus xylophilus isolate was inoculated on one-year-old resistant and susceptible seedlings of Pinus thunbergii respectively, and nematode dispersal and water potential were studied thereafter. Results showed that, at the initial stage the number of nematodes was small and nematode dispersal rate was low. Most passing nematodes in resistant seedlings were downwards and the number was distinctly smaller than that in the susceptible. Passing nematodes in a susceptible were both upwards and downwards, and nematode dispersal rate and number of the downwards were significantly smaller than those of the upwards. Later, the nematode dispersal rate rose when nematodes began to propagate. The result of conduction in water potential showed that both the susceptible and the resistant had the same variation in the values, in which they rose first then got down but rose again at last. This study might provide some guides for histopathology studies on pine infected by B. xylophilus.