Based on the method of incubation test and controlling the pH of typical black soil samples, the relationship of soil pH and the effective content of trace elements of Cu, Zn and Mn was studied. The results show that following pH changing 0.5 units, the ratio of high value to the low value of the effective Cu content is about 0.5~1 times in typical black soil, the ratio of effective Mn content is about 3~5 times and the ratio of effective Zn content is about 9~15 times. These indicate that it is great importance of theory and practice for soil diagnosis, proper fertilization of trace elements fertilizer, increasing grain output and realizing sustainable utilization of land that pH value of soil is mastered accurately.