Based on central plant hot recycling, the influence law of density differences between reclaimed asphalt pavement(RAP) aggregate and new aggregate on the void ratio and gradation of the hot mixture was studied. The test method for mineral aggregate density of the RAP was improved. The hot recycling mix void ratio rule and generalized gradation rule were put forward. With fixed use level of the RAP and asphalt aggregate ratio, the smaller the bulk density of mineral aggregate, the greater the porosity. On mixture gradation curve, the part of the curve affected more by aggregate with low density shifts to upper limit gradation, the part of the curve affected more by aggregate with high density is close to the lower limit gradation. The aggregate density fluctuations must be strictly controlled in asphalt pavement construction.