This study includes the effect of wafer resistivity and intensity  of light on topography of porous silicon surfaces which produced by photo chemical etching method, the results showed that changing of the resistivity led to change the  porosity, where it found the porous silicon layer be less of high value resistivity.  Once all the wafers have same resistivity's value that’s found the light intensity effect on porosity, the less value of porosity produced by the less value of intensity light focused. The production of Nano crystalline silicon structures and control of their production conditions is the first step to control the properties of the devices (detectors, diodes, solar cells, sensors) and their appropriate applications. Ultimately, this is important in promoting research and development of renewable energy.