The operational status of Wastewater Treatment Plant (WWTP) A in Tianjin was simulated via WEST 2012 software. It was found that with secondary biological treatment, the chemical oxygen demand (COD), ammonia nitrogen, and total nitrogen in the effluent can reach Level 1‐A standards, while the total suspended solids (TSS) and total phosphorus slightly exceed the standard threshold. When subjected to the maximum water volume during the rainy season and the most unfavorable temperatures in winter, WWTP A can maintain the same treatment conditions as under normal circumstances. Meanwhile, an operational performance evaluation index system of the WWTP was utilized to evaluate the operating conditions. The result indicates that WWTP A achieves a good performance level, with some aspects that need to be improved. Among them, technical requirements, equipment advancement, energy consumption, water consumption, and chemical consumption are less satisfactory; these issues are mainly due to the process and equipment selected for the WWTP. In order to improve the comprehensive operational performance of the WWTP, it is recommended to add a water reuse system, strengthen the management of the energy consumption department, and adopt high‐efficiency energy‐saving equipment.