In the present work, a photoelectrochemical etching method had been performed on resistive p-type Si (100) to eliminate the instability attributed to the high resistivity of substrate comparing to that of electrolyte. The anodization of p-type Si with resistivity ranging from 10 Omega cm to 30 k Omega cm was done in HF/ethylene glycol. The resistivity of electrolyte was experimentally determinated by high frequency impedance measurements. As anodization proceeds structures of increasing characteristic size are formed then a steady state is reached, where macropore grow parallel. It shows that pore diameter increases with increasing HF concentration. Whereas, under laser He-Ne irradiation both of nanopores and macropores are observed during the anodization. The nanoporous layer showed to be varying with the light intensity and the anodization time. The proprieties of the porous silicon were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and energy-dispersive X-ray (EDX).