Abstract: In this paper, a model for internal floating roof tank is established to study the potential distribution on various metal components of internal floating roof tank and its influencing factors, and thus discharge locations of the tank and preventive measures are determined in case of lightning, and the experimental data of potential distribution on different locations of the storage tank and the current flow direction of discharge cable through performing lightning simulation test of internal floating roof tank are obtained. The results show that in the case of a lightning surge, there is no current passing through the static electricity discharge cable, thus the potentials of floating disc and tank top are the same, the overall potential of the tank can be up to hundreds of kilovolts, which will easily cause discharging to metal components that are not in equipotential connection and thus led to accidents. Based on this conclusion, the reduction of earthing resistance can decrease the potential of storage tank in case of lightning, and equipotential connection can eliminate the occurrence of fire accidents of the tank due to lightning. These research results have certain instructive significance for improving lightning protection measures of internal floating roof tank.