With the continuous improvement of infrastructure, the issue of internal damage in the semi-rigid base layer structure of heavy traffic highways is becoming increasingly prominent. Particularly, the maintenance and reinforcement of semi-rigid base layers represent one of the urgent challenges that need to be addressed. Based on the South China Expressway project, the effectiveness of semi-rigid base layer grouting reinforcement was investigated. Five different grouting materials were used to treat the internal structure of the road surface. Three-dimensional ground penetrating radar and a falling weight reflectometer were combined to assess changes in internal damage and load-bearing capacity before and after grouting. Simultaneously, a evaluation system was constructed to assess the internal structure of the road surface treated with grouting,and analyze which grouting material achieves the best reinforcement effect based on indicators such as crack reduction coefficient(CRC), carrying capacity improvement coefficient(CIC) and repair uniformity coefficient(RUC). After evaluation, the grouting reinforcement effectiveness on the internal structure of the road surface by the five grouting materials is as follows: high-strength polymer(with waterproofing agent)>high-strength polymer(without waterproofing agent)>low-strength polymer(with waterproofing agent)>geopolymer>low-strength polymer(without waterproofing agent).