Hydrothermal etching method is employed to prepare four Iron-passivated porous silicon (IP-Si) samples of different etching time. The sponge-like morphology of the samples is observed by scanning electron microscope (SEM), and larger diameter difference of etching holes and lower morphology smooth are found as a result of increasing etching time. Under 250 nm excitation, all samples emit strong orange light with peak around 620 nm and full width at half maximum (FWHM) of 130 nm. And no correlation between photoluminescence peaks and etching time is found. Together with the result of Fourier transform infrared spectroscopy study, the physical mechanism for the photoluminescence of IP-Si is interpreted by using the quantum confinement-luminescence center model, and the non-bridging oxygen hole center is ascribed as the radiative recombination luminescence center.