Nanosecond pulse laser electrochemical etching can remove the electrolytic products of laser irradiated region and so improve the processing stability and processing efficiency. The stress-etching characteristics and the material removal mechanism for aluminum alloy workpiece were investigated theoretically and experimentally by the use of a laser electrochemical machining system. For comparison of processing topography between laser direct etching in air and laser electrochemical machining, the scanning electron microscopy and the optical profilometry were used to detect and analyze etching morphological characteristics of machining areas. Based on the principle of mechanics and electrochemistry, stress-etching principles of laser electrochemical machining were studied. In this study, the effects of processing parameters and machining method on machining quality were explored, and a complex microstructure was processed successfully with reasonable processing parameters. The results show that laser electrochemical machining with better stability can reduce surface roughness and improve machining quality effectively.