Optical properties of trap pit morphology of multicrystalline silicon (weaklyetched, normaletched and heavyetched) were simulated by solving the Maxwell and material equations, using RF MODULE of COMSOL Multiphysics version 3.5a. The varying laws of surface electric field a component, surface magnetic field y component and reflectivity of three kinds of trap pits were obtained. It is indicated that the value of surface electric field z component and surface magnetic field y component of weaklyetched trap pit is the least, and its reflectivity is the highest(about 35%)at wavelengh of 600nm; followed by that of normaletched trap pit, its reflectivity is about 17%; the value of surface electric field z component and surface magnetic field y component of heavyetched trap pit is the most, its reflectivity is the lowest(about 10%). Compared the experimental date with the simulation results, change trend of numerical simulation results are accorded with that of experimental ones, which provided for the practice production of acidic texturing of multicrystalline silicon as theory bases.