Abstract: Abstract: With the purpose of evaluating the effect of prescribed burning on the burning performance of undergrowth plants of pure Pinus Yunnanensis forest, the pure Pinus Yunnanensis forest in Zhaobi mountain, Xinping County, Yuxi City, Yunnan Province, with an interval of three years after the planned burning was selected as the study plot. In this article, the three plots were set in each group with prescribed burning as the variable. Three sample plots were set in each group,resulting in a total of six sample plots. The study contains field investigation, observation, sampling, experiment, and analysis of experimental data. The influence of whether or not conducting prescribed burning on the characteristics of species change,combustibility and fire behavior of fuel under forest was explored、 The research demonstrated that： The prescribed burning reduced the number of species in the herb layer of Yunnan Pine Pure Forest but had little impact on the growth status of mature Yunnan Pine, and the number of trapezoidal combustibles could be reduced by prescribed burning. After three years of planned burn recovery, the ignition point of combustibles under the forest has decreased. The calorific value of pine needles of the main surface combustibles has increased, the ash content has decreased, and it has become more flammable. Prescribed burning can decrease the surface combustible material load, reduce the flame duration and height, significantly reduce the spread rate of surface fire, and curb the possibility of canopy fire.

Key words: Key words: prescribed burning, Pinus Yunnanensis, understory plants, combustibility, fire behavior