Three essential factors of forest fire (fire source, environment, and litter) were taken as the point of view, and has approached the forecast method of forest fire in tropical area of southwest China in a macroscopic scale. This study supported by mathematical method was from a new angle. For example, in the aspect of forest fire forecast, it has been thought over that most forest fire is artificial fire, which has lots of randomness. So it could be studied in a kind of Markov random processes. In the aspect of the analysis of environment that leads to forest fire, correlation analysis would reveal the relation among cosmos, earth and life, for instance, the relation between E1 Nino (or La Nina) and forest fire. Especially in the aspect of estimating the amount of litter, a new estimation method based on spacial remote sensing data was raised. It provides an effective and quantitative way with higher reliability for forest fire forecast on region scale. Three essential factors of forest fire (fire source, environment, and litter) were taken as the point of view, and has approached the forecast method of forest fire in tropical area of ​​southwest China in a macroscopic scale. This study supported by mathematical method was from a new angle. For example, in the aspect of forest fire forecast, it has been thought over that most forest fire is artificial fire, which has lots of randomness. So it could be studied in a kind of Markov random processes. aspect of the analysis of environment that leads to forest fire, correlation analysis would reveal the relation among cosmos, earth and life, for instance, the relation between E1 Nino (or La Nina) and forest fire. Especially in the aspect of estimating the amount of litter, a new estimation method based on spacial remote sensing data was raised. It provides an effective and quantitative way with higher reliability for forest fire forecast on region scale.