Four kinds of programs for mixing the old asphalt layer and semi-rigid base milling material were designed for the cement stabilized full-depth in a situ regeneration base.Through indoor and engineering field tests,the relationships between the thickness of the cement stabilized full-depth in the situ regeneration base and the content of old asphalt layer were discussed.The results show that when the deflection of the original pavement base is greater than 100(0.01 mm) and the mass ratio of the old asphalt layer over the regeneration base is less than 27%,the thickness of full-depth in the situ regeneration base should be controlled between 18 cm and 25 cm.While the deflection of the original pavement base varies from 80(0.01 mm) to 100(0.01 mm) and the mass ratio of the old asphalt layer over the regeneration base is between 27% and 50%,the thickness of full-depth in the situ regeneration base should be controlled between 15 cm and 22 cm.According to the content of the old asphalt layer,the thickness of the cement stabilized full-depth in the situ regeneration base can be controlled and the regeneration base quality can be ensured.