The paper took gap rate of coarse aggregate as an evaluation index of the second foamed asphalt recycled mixture skeleton degree,and analyzed the influence factor of coarse aggregate gap rate by different proportions of foam asphalt cold recycled mixture coarse aggregate size group based on the grey correlation entropy method. Result showed that the influence degree of the coarse aggregate from the large to small is 19-26.5 mm, 4.75 to 9.5 mm and 16 to 19 mm, 9.5 to 13.2 mm and 13.2 to16 mm;in the gradation design,the paper got the excellent performance of the foam asphalt cold recycled mixture skeleton by rationablely adjusting the proportion of different sizes of gravel;when the five coarse aggregate ratios of 4.75 to 9.5 mm, 9.5 to 13.2 mm,13.2 to 16 mm, 16 to 19 mm, and 19 to 26.5 mm are 32.55%, 19.60%, 13.70% and 11.15%, 15.29%, 7.73% respectively.The structure of aggregate is the most stable.By analyzing the difference between grey correlation entropy value,it got the main mineral aggregate particle size range and key mesh of second foam asphalt cold recycled mixture skeleton structure.