A 1.3 μm high-speed directly modulated semiconductor laser based on AlGaInAs material is designed. The designed laser uses the ridge waveguide structure, the cavity with short length and eleven multi-quantum wells with thickness of 5 nm combined with the graded index separate confinement heterostructure (GRIN-SCH) with thickness of 30 nm to achieve laser output with low threshold, wide bandwidth and high power. A stable single longitudinal mode output is achieved by using uniform grating and asymmetric cavity surface coating. Based on the 1.3 μm high-speed directly modulated semiconductor laser at room temperature, the threshold current is about 7.5 mA, the 3 dB small signal modulation bandwidth can reach 25 GHz, the large signal back-to-back transmission rate can reach 40 Gb/s, the slope efficiency is 0.35 mW/mA, the maximum output power is about 39 mW, and the side mode rejection ratio can reach 40 dB.