The present disclosure provides a method for detecting resistance of a photo resist layer. The method includes: providing a silicon wafer and measuring a refractive index of a surface of the silicon wafer as an initial refractive index of the surface of the silicon wafer; forming photo resist layers with different thicknesses on the surface of the silicon wafer; performing ion-implantation on the photo resist layers by predetermined amounts; peeling off the photo resist layers from the surface of the silicon wafer; and testing the refractive indexes of different areas on the surface of the silicon wafer after the ion-implantation, on which the photo resist layers with different thicknesses are located and determining the resistance of the photo resist layers with different thicknesses in contrast to the initial refractive index before the ion-implantation.