The model of preserving a format encryption scheme based on a Feistel structure has developed rapidly and has been widely used in recent years. In this paper, the software implementation of the FF1 algorithm for the model was presented, and its execution efficiency was evaluated. Then, the efficiency bottleneck problem and its causes were identified. Based on the above analysis results, optimization methods were given from the perspectives of prepossessing, algorithm structure, and format conversion function, and implementation plans were provided. Finally, the simulation results show that the optimized performance improvement is significant, and the degree of performance improvement increases with the increase in plain text length.