Multi-Pulse Rectifier pulse has been widely used in electrolytic aluminum and DC traction power supply system of metro due to high output power quality and low harmonic distortion of the input AC line current. A math method based on 24-pulse rectifier system with stretch triangle connection at the primary side of the transformer is used to accomplish 48-pulse rectifier system. The tap ratio to realize 48-pulse rectification is obtained through this math method. The input AC line current and circulating current is analyzed by MATLAB/Simulation.The results shows that ideal 48-pulse rectification can be achieved by two-tapped inter-phase reactor , at the same time the input AC line current harmonic is suppressed and the THD is reduced.