According to the characteristics of differences between the changes of accumulating sucrose of sugar-cane variety in different mature period and the high sucrose content pened,the model of sucrose content acumulation of development has been used to analyze the relationship between the combination form of different mature period and the sucrose content in crushing season. The effect of the rational compose of the different mature period on lengthening high sucrose content period and cultivation of average sucrose content in the crushing season is revealed theoritically. The calculation principle and way of plant ratio is given. The guiding basis for Sugar Mill defining the plant ratio of the different mature period variety is provided and the economic benefits could be improved.