[Objectives] In order to set or improve the lightning protection measures of ships, it is necessary to evaluate the strike risk of critical equipment and the protection effect of the lightning rod. [Methods] In this paper, a lightning leader fractal model is constructed and applied to the simulation study on the lightning attachment process of a ship. The configuration method of the simulation boundary of the model and the quantitative evaluation method of lightning strike risk are improved, and a quantitative study on the influence of different factors on the lightning strike risk of the ship is performed. [Results] The simulation results show that the protection probability of the lightning rod in the middle of the ship is more than 75% under the basic configuration. The bow, stern and the antenna far away from the lightning rod have a relatively large risk of circling strike. The lightning strike probability of the shipboard antenna will be lower if the lightning initiation position is closer to the lightning rod, the lightning current is greater or the lightning rod is higher. [Conclusions] The lightning leader fractal model constructed in this paper can be used to investigate the weak links of direct lightning protection on the surface of ships, which is helpful to the protection design of the direct lightning for ships.