Abstract: Aiming at the poor effect of waste water treatment process in sand and gravel system, field wastewater of 2 processing systems for sand and stone in Baihetan Hydropower Project and Wudongde Hydropower Project was sampled. And then the numerical simulation, field and laboratory experiments were conducted to optimize the main wastewater treatment process. Experiment results show that total recovery rate by two-step stone-powder recycling can reach to about 60%, an improvement to single-step recycling by 50%; sedimentation performance can be significantly improved by adding suitable flocculant, if the particle size of suspended solids was small, the co-conditioning technology with PAM and CaO should be applied, and the hydrostatic settling velocity is improved by 11 times. The agent used in wastewater sedimentation and slurry dewatering have much consistency in type and dosage of front-end sedimentation process, so the technology of only adding flocculant in front-end sedimentation process is feasible. The technique of diaphragm pressing and high pressure air flow were introduced into filter press, then dewatering time has been decreased by 67%, and moisture content of the powder cake has been reduced to 15%.