Distributed generation (DG) technology has been rapidly developing and the DG penetration level is becoming higher and higher in power system distribution network in recent years. Due to the access of multiple distributed generators, the traditional instantaneous overcurrent protection may fail to coordinate with each other. In order to solve this problem, this paper studies the fault characteristics of distribution network with high DG penetration and analyses the effect of voltage to protection during faults. Based on the existing adaptive instantaneous overcurrent protection, this paper introduces a voltage acceleration factor, which improves the coordination between protection devices. The 10kV distribution network is used to validate this algorithm. Simulation results demonstrate that the proposed adaptive instantaneous overcurrent protection is efficient.