Porous silicon nanowires (PSiNWs) layers fabrication was reported. Reflectance spectra were measured as a function of the nanowire length and were inferior to 0.1% and a strong photoluminescence (PL) signal was measured from samples. Models based on cone shape of nanowires located in circular and rectangular bases were used to calculate the reflectance using the Transfert Matrix Formalism (TMF) of PSiNWs layer. The modeling of the reflectance permits to explain this value by taking account into the shape of the nanowires and its porosity. Optical absorbance and transmission were also theoretically studied. The absorbance was superior to that obtained with silicon nanowires and the ultimate efficiency was about equal to 25% for normal incidence angle. These results could be applied to the potential application in low-cost and high efficiency PSiNWs based solar cells.