Abstract: 【Objective】 Provide theoretical support for the development of long-term breeding strategies and elite varieties for masson pine(Pinus massoniana). Additionally, the changes in genetic diversity and gain of Guangxi masson pine in the breeding process were analyzed, and the feasibility of obtaining improved effects by the design of breeding population structure and the selection method was discussed. 【Method】 The genetic diversities of the natural, first-generation, 1.5-generation and second-generation breeding populations were analyzed by the SSR molecular marker technique. The corresponding genetic gains were estimated basing on the genetic test results. 【Result】 In the first-generation of genetic improvement, the gain of wood volume and loss of low-frequency alleles for masson pine were approximately 32% and 14%, respectively. The Shannon diversity index(I)remained unchanged, but the observed heterozygosity(H_o)increased nearly 27%. In the 1.5-generation of genetic improvement, the gain of wood volume and loss of low-frequency alleles were 19.34% and 16%, respectively. The I and inbreeding coefficient decreased 6% and 20%, respectively, whereas H_o remained unchanged. In the second-generation of genetic improvement, the gain of wood volume and loss of low-frequency alleles were 23.68% and 12%, respectively. The I, H_o and inbreeding coefficient decreased approximately 25%, 20% and 47%, respectively. 【Conclusion】 During the three processes of genetic improvement of Masson pine in Guangxi, the genetic gain was high, and the loss of genetic diversity was relatively low. The degree of inbreeding was also effectively reduced. It is suggested that the selection strategy was effective in striking a balance between the genetic gain and genetic diversity.