The failure of the key parts, such as bearings and gears, in cutting drum long chain gear driving system of long-wall shearer is a crucial factor for service life of gear systems. A short driving system is driven by multiple electric motors for cutting drum has been proposed as an alternative to long chain gear driving system. An electromechanical dynamic model based on lumped-parameter method of short driving system is established considering the effect of intrinsic mechanical characteristic of electric motor. By taking into account time-varying stiffness, damping, electric motor synchronization error, manufacturing eccentric error and transmission error of gears, the load-sharing characteristic and dynamic characteristic of the multiple motor driving unit (MMDU) of short driving system are analyzed under shock load. The results of simulation show that the electric motor synchronization error has significant effect on the load-sharing characteristic of MMDU. The load-sharing coefficient evidently increases as the electric motor synchronization error go up, decreasing the electric motor synchronization error can improve the load-sharing characteristic of MMDU; and the synchronization error must be controlled fewer than 5 % to ensure the load-sharing coefficient of the MMDU under 1.1. The imbalance of dynamic meshing force distribution of pinions of the MMDU can be obviously decreased and the load-sharing characteristic of the MMDU can be greatly improved by controlling the synchronization error of electric motor, but the effect is unobvious by controlling the manufacturing eccentric error or transmission error. It provides an effective method to choose a suitable control ranges under different synchronization errors of electric motor according to different load-sharing requirements for the MMDU.