To meet the application requirements of permeable pavement with high permeability， three kinds of continuous gradations with large void ratios of gravel and gravel with sand are designed， as well as three kinds of single-grain gradations of gravel. The crushing value of gravel with different gradations are tested. The corresponding mechanism of the effect of gradation on crushing value and the change in particle size after crushing are analyzed. The test results show that： The increase in crushing value of saturated gravel is positively correlated with the content of small-size gravel； 7.1% sand can improve the crush resistance of gravel； the reduction effect of large-size gravel on the crushing value decreases with the increase of the particle size. The critical particle size theory and inference on the crushing value are proposed. It is found that if the gravel with particles is larger than 9.5 mm account for more than 59.6% of the content and the maximum size of the particles ranges between 19—26.5 mm， the crushing value of the graded gravel with a large void ratio can be effectively improved. The demarcated particle size hypothesis and concept of equivalent and discount transformation of gravel content of the crushing value are proposed. Based on the above theory， inferences， hypothesis and concept， a set of calculation formulas for crushing values with the average error of 57 examples within 2.4% are designed. The calculation model can be further used to estimate the crushing value of various material gravel with large void ratio and particle size greater than 2.36 mm which has continuous， intermittent or single gradation with no characteristics of the single particle size. The calculation model improves the design efficiency of gradation with large void ratios in the base of permeable pavement.