Ungulate depletion is a major factor driving the current decline of wild Amur tiger Panthera tigris altaica. To conserve this globally threatened species, we should monitor their prey densities timely. It is often desirable to estimate absolute densities of prey population across large areas for effective tiger conservation and management. However, determining absolute density is complex and often controversial. Ungulate are notoriously hard to completely or partially survey using direct counts in Northeast China for rare sightings, poor visibility in dense forests, manpower and budget limit and surveyor must rely on indirect snow signs. For this reason, the line transect methods often are used to census ungulate density in winter. Several indirect sampling methods of them have been proved to be cost-effective, repeatable and objective, but other indirect counting methods are frequently unreliable and usually require independent calibration or confirmation. On the basis of the stratification sampling principle, from January, 2002 to March,2004, the population density status and dynamic trends of three main Amur tiger's prey species (i.e., wild boar (Sus scrofa), red deer(Cervus elaphus)and roe deer (Capreolus pygargus)) were investigated as a prey baseline data for tiger conservation in eastern Wanda Mountains, one of the main Amur tiger population distribution regions in northeastern China, by using Sample Plot Method recommend by experts from America, Russia and China. This survey method was conducted as followings: During a single day, 5 teams of fieldworkers simulataneously walked 5 parallel transects, the length of each transects is at least 5 km and the interval transects is about 500 m, within one plot to provide complete coverage. Together, we surveyed 53 pots with the total sampling areas was 557.7 km² which occupied 10.34% of the total study area (5392.65 km²) and 265 transect with total survey effort about 1325 km. Our results suggested that the highest mean population density of the three preys of Amur tiger is that of roe deer ((0.4980 ± 0.0436) individuals /km²); Second is that of wild boar ((0.3423±0.0275)individuals/km²); The lowest is that of red deer ((0.2010±0.0270) individuals /km²). Using one-way ANOVA, we demonstrated that the density of each ungulate species is significant different in the mixed broadleaf stand, shrubs and shaw stands. There were also significant differences in the density of three ungulate species in different habitats. Spearman Rank correlation showed that the positive correlation between the population density of red deer and wild boar existed. The mean annual decreasing ratio of red deer, rod deer and wild boar was 13.48%, 12.69% and 1.89%, respectively in this region from 1989 to 2002. Prey scarcity affects Amur tiger by decreasing the proportion of productive females, delaying the age of first reproduction, reducing litter size, increasing offspring and adult mortalities, expanding home ranges, intensifying movements and increasing the numbers of transients and dispersing individuals. Thus, recovery and effective management of ungulate populations is a prerequisite to tiger conservation in eastern Wanda Mountains. The larger decline of main prey of Amur tiger can most likely be attributed to intensive poaching that occurred and still occurred throughout the eastern Wanda Mountains. Future conservation measures should stop this.