A low-cost acid leaching process is studied in this paper to prepare solar-grade polysilicon. The effects of process conditions (grain size, acid species and concentration, leaching time and temperature) are discussed. The further optimized conditions by orthogonal experiments are given in this paper. Optimal operating conditions are suggested: 75μm of grain size, 80 min of leaching time, 0.28 mol/l of concentration of HF, 80 C of leaching temperature. The removal efficiency of impurity reaches 98.41%. Analysis by ICP-AES and SEM illustrates acid leaching appears to be a potential primary process for solar-grade Si purification. .