Aimed at the starting condition of light hybrid diesel engine with ISG technology in normal temperature, the working models of diesel engine and ISG electromotor were established. Then, the diesel engine moment of resistance on the starting condition was calculated to obtain the torque and the power from the ISG electrical machinery. And, the simulation to the starting process was carried out. Finally, the test of the ISG electromotor dragging diesel engine under the different voltage was performed to confirm the simulation result. The results showed that with the ISG technology, the diesel engine can be dragged to meet the requirement speed on the battery voltage of 36～60V. The average starting torque of ISG motor is 87.4N?m, the line current of each start winding is 30～150A. and the output power of ISG fall after the first increase with the peak power of 4.98kW. The simulated starting time from 0 to fire is 0.4s, compared with the test result of 0.5s; while time from 0 to stable idling in the simulation is only 2.8s, the test result is 3.1s. So, the test result is tallied with the simulation.