Since conventional electro-mechanical converter of 2-D digital valve had limitations of large inertia and low dynamic response, a low inertia rotary electromagnet with coreless rotor structure was proposed. Based on magnetic circuit approach, the influence of key structure and operating parameters on the output torque of electromagnet was discussed firstly. Then the finite element simulation of torqueangle characteristic was performed on the platform of Ansoft/Maxwell 3-D. The experimental results were in a close agreement with the simulated results. The low inertia rotary electromagnet had large static torque and its torqueangle characteristic was close to sinusoidal waveform, which would be used as electromechanical converter of 2-D digital valve with high frequency response.