The invention provides a semiconductor laser suitable for the technical field of lasers. The semiconductor laser comprises a substrate, as well as a buffer layer, an N type limit layer, a lower limitlayer, a lower waveguide layer, a multi-quantum well, an upper waveguide layer, an upper limit layer, a corrosion blocking layer, a P type limit layer and an electrode contact layer arranged on the substrate from bottom to top, and at least two expanded waveguide layers are arranged between the buffer layer and the N type limit layer. Thus, the vertical divergence angle can be reduced while the coupling efficiency is improved.