Abstract: Tending and transforation of man-made forest is an important forest practice to accurately improve forest quality. In order to evaluate the effects of tending and transformation on the low yield and low efficiency forest of high-density Pinus armandii, the high-density Pinus armandii with low-yield and low-efficiency plantation in Group 5, jian shan village, Taiping Town, Huili County was transformed. The growth of trees, the change of stand fruit setting, the impact of biodiversity, water and soil conservation were investigated after six years of low-efficiency stand transformation. The results showed that the thinning and tending of the low-yield and low-efficiency Pinus armandii plantation could not only promote the growth quality of Pinus armandii stands, but also increased the seed yield of Pinus armandii by at least 3.5 times in a short period of time, and promoted the forest biodiversity and soil and water conservation capacity.