The studies for detects compensation and doping of LPCVD grown a-Si materials have been made by ESR, σD, σph, SIMS and Eα measurements. It is found that these materials can still be doped, although with no detectable hydrogen content. In particalar, the films can be doped effectually, and the Fermi level can be moved obviously toward the band edge in the heavily doped zone. In this paper, based on the new point of view about a-Si doping presented by Street recently, the mechanism for a-Si doping without hydrogen is explained in terms of defect compensation and chemical coordination.