The electrochemical etching process of porous gallium phosphide was studied by means of the characteristic current–potential (I–V) curves. Measurements were performed in H2SO4 0.5‐M aqueous solution both in the dark and by illuminating the samples with the 351‐nm line of an argon laser. Raman spectroscopy was applied to investigate the surface morphology of the samples prepared under different anodizing conditions within the potentiostatic regime. Based on a few reasonable assumptions, a simple model of pore growth is proposed. The enhancing effect in current intensity due to the branching of pores and the opposite effect due to a concomitant decrease in the effective cross area available for carrier transport are accounted for to explain the main features of the recorded I–V curves.