In order to solve the problems of the shortage of waste slag resources, the difficulty of Engineering abandoned earthwork and the outward transportation of bored pile mud, and realize the resource utilization of Engineering abandoned earthwork and mud, five processes are used for field comparative tests, and the research on the replacement of traditional waste slag as subgrade filler by cushion cap excavation earthwork and bored pile mud solidified material is carried out. The results show that inorganic materials with a mix ratio of 3% cement + 1% mineral powder + 5% lime are selected as the main curing materials. Under the condition that the amount of solidified material remains unchanged, the water stability of solidified backfill subgrade is better than that of the one-time lime mixing method by using the secondary lime mixing and the sludge soil site solidification construction technology without strong mixing head. The application of this technology can effectively solve the problem of shortage of slag supply, reduce environmental pollution and save construction costs on the premise of ensuring the use function of the road.