According to the highway subgrade engineering construction period serious delaying by rainy climate for a long time in the tropical rainy regions. The key process of the subgrade construction affected by climate is roadbed filling turning. Binding the law of rainy, Considered the continuous available period for filling turning as a random variable to analyze the correlation with its frequency, established the regression formula, the values of correlation coefficient is more than 0.95, shows that the continuous available period for filling turning presents good exponential relationship, A new statistical method of continuous available period for filling turning called selecting time construction concept was put forward. According the feasible probability of the continuous available period for filling turning, put forward a new grade division method for roadbed filling. Optimized the construction organization of the subgrade engineering by the statistical function of continuous available period for roadbed filling turning, and proved its reliability and achievability. Demonstration and reference were provided for the highway construction and local standardization in southern rainy regions.
