A porous silicon microcavity (PSM) is highly sensitive for sensing applications due to its high surface area and a narrow resonance peak. In this letter, we fabricated the PSM by alternate current density from a low value to a high value during double-tank electrochemical anodization at different electrolyte temperatures. Results show that with the increase of the electrolyte temperature, the rate of the PS etching becomes faster and the refractive index of the PS layer becomes smaller. The thickness of the PS increases faster than the decrease of the refractive index of the PS.