Compact optical beam splitters are important for enhancing the performance of integrated photonic system or developing new applications. A compact beam splitter based on a tapered multi-mode interference structure was proposed according to the self-imaging theory. Firstly, the optical performance of the beam splitter was simulated by time-domain finite difference method, and the optimized structure parameters were obtained after maximizing the transmission efficiency: the tapered waveguide length was 20 μm, the multi-mode interference waveguide length was 3.8 μm, and the gap width was 0.50 μm. Secondly, the beam splitter with the optimized structure parameters was simulated and analyzed. The results show that in the wavelength range from 1 480 nm to 1 610 nm, each output has a low loss of more than ?3.46 dB while the energy difference between the two splitting paths is less than 0.1%. Finally, the designed device structure was processed and experimentally tested. The results show that, at the wavelength of 1 581 nm, the loss of the two channels of the beam splitter reaches the minimum values, which are ?2.31 dB and ?4.83 dB, respectively. The device has a simple structure and has major advantages in terms of integration, device fabrication and low cost, which has promising applications in integrated photonic systems.