The effect of back surface etching on power conversion efficiency in multi-crystalline silicon solar cells is explored.The experimental results sho w that the short-circuit current is improved by the etching,and the power conve rsion efficiency is increased by 0.1%.Before or after the etching,the scanning electron microscope (SEM) morphology,the reflectance spectra of back surface an d the external quantum efficiency for multi-crystalline silicon solar cells are investigated to understand the enhanced power conversion efficiency.It may be attributed to that the etching leads to a "mirror" back surface in multi-crysta lline silicon solar cells,which is beneficial to solar photons internal reflection and aluminu m paste contact with the back surface.The back surface etching is an alternative up-gr ade process for production line of multi-crystalline silicon solar cells.