A 1.31 μm square-Fabry-Perot (FP) coupled cavity semiconductor laser is theoretically analyzed and experimentally prepared. The square cavity acts as a reflection end for the FP cavity, and its reflectivity is adjustable by changing the current injected into the square cavity. The mode coupling between the square mode and the FP mode can suppress other side modes, and it is easy to realize single-mode lasing. The maximum single-mode lasing side mode suppression ratio obtained in the experiment is 38 dB, the wavelength tuning range is 6 nm, and the estimated characteristic temperature T0 is 46 K.