Abstract: Analysis of electromagnetic characteristic for three-phase induction motor transient process is fundamental to protection of mine electronic products against electromagnetic interference. The transient process of belt motor was analyzed by ATP software. Then, the propagation characteristic of transient pulse in tunnel and cable was researched by transmission line theory. The results indicate that motor starting, braking and load sudden change can all produce transient pulse, which peak voltage is six times rated voltage, and peak current was closed to eleven times rated current. Its radiated emission plays only a small part in the real effect on the electromagnetic environment in belt conveyor tunnel, and long cable has nature attenuation function for transient pulse propagation in it. The instrument of measurement and test point location in coal mine were confirmed. Comparing the measured data with the theoretical value, the results show that the transient radiation disturbance in belt motor starting and braking process can be ignored. Transient conduction disturbance voltage is larger, but pulse peak does not exceed the rated value of four times. So, the research results present useful reference for the electromagnetic compatibility studies in mine.