Abstract: In the wet temper rolling process of a double-stand mill, insufficient control of process lubrication may induce strip flatness defects, such as edge waves, center waves, and compound waves. Considering the equipment configuration of the double-stand temper mill and the process characteristics of wet temper rolling, this study established calculation models for entry and exit tensions and analyzed the influence of wet temper lubrication parameters on exit strip flatness. By introducing the heat transfer coefficient during wet temper rolling as an intermediate variable, the relationship between process lubrication parameters and the friction coefficient was established, and influence functions of temper fluid concentration, temperature, and flow rate on strip flatness were developed. In combination with actual production conditions, the investigated ranges of key process lubrication parameters were determined. With the objective of minimizing finished strip flatness fluctuation while ensuring stable mill operation, the concentration, temperature, and flow rate of the temper fluid were comprehensively adjusted, and a process lubrication optimization technology suitable for double-stand wet temper rolling was developed to improve finished strip flatness control. The proposed technology was applied to the actual production of typical steel grades and specifications on a domestic double-stand wet temper mill. The flatness value of the strip at the temper mill exit decreased from 13.2 IU before optimization to 6.5 IU after optimization, demonstrating an effective improvement in the flatness control capability of the double-stand wet temper mill.