In order to improve the characteristics of TFT, 4-mask PR ashing process was carried out by indu cti vely coupled plasma etcher. After PR strip, linear a-Si film residue appeared on the edge of source/drain data line,TFT channel and other pixel area. The effect of PR ashing conditions on a-Si film residue was studied. The results show that the pressure and Bias RF power are the main factors to produce the film residue, and the amount of O2 is the secondary factor. By adjusting the PR ashing recipe, the optimal condition for preventing film residue is obtained: Pressure ≥ 2.66 Pa, Source power∶Bias power ≥ 3∶1, qv(SF6)∶qv(O2) ≥ 1∶60. The research of inductive coupling plasma etcher in PR ashing process has very important significance for the further application.