The utility model discloses a system for measuring magnetic characteristics of a silicon steel sheet under excitation of a PWM power supply. The system comprises a control computer, a data acquisition card, a low-pass filter, a power amplifier, an isolation transformer, a magnetic yoke, an excitation winding, a laminated wood padding block, a coil bracket, a protective sleeve, a magnetic flux density measuring coil, a coil insulation framework, a first magnetic field intensity measuring coil and a second magnetic field intensity measuring coil, wherein the excitation winding is connected to the isolation transformer, the magnetic flux density measuring coil is connected to the data acquisition card through a first isolation amplifier, the first magnetic field intensity measuring coil is connected to the data acquisition card through a second isolation amplifier, and the second magnetic field intensity measuring coil is connected to the data acquisition card through a third isolation amplifier. The system disclosed by the utility model is simple in structure, the winding is low in processing difficulty, an air compensating coil is saved, and the manufacturing cost of the system is reduced.