Nuclear power has high requirements for related equipmentdue to its radioactivity. Packing seal is a dynamic sealing method widely used in nuclear power machinery between holes and axles. The greater preload force on the packing seal, the better the sealing effect, but the wear rate will increase, shortening the service life. Therefore, the study of the influence of preload on wear and leakage has been analyzed in this paper. The mapping model for determining the relationship between preload and the leakage rate, as well as the service life were established. The key parameters of the model were identified based on experimental data. The final model of wear and leakage was obtained. Finally,the accuracy of the revised model was verified by experiments.