Abstract: In the strength optimization of composite scarf repair, the widespread use of finite element (FE) method has led to inefficiencies, and studies on multi-parameter cooperative optimization are also lacking. To overcome these issues, this paper introduces a multi-parameter cooperative optimization program (CRPOP) for composite stepped-lap repair (CSLR). The program replaces FE method with a combination of theoretical and analytical approaches, yielding a semi-analytical solution for adhesive layer stress. Also, it performs cooperative optimization on repair patch layup and step length, utilizing the genetic algorithm. Results indicate that CRPOP can perform both single and multi-parameter optimizations for CSLR structure, reducing maximum adhesive shear stress by 28.3% and 30.8%, and increasing structural load capacity by 20.4% and 25.2%. It demonstrates that the program effectively mitigates stress concentration in the adhesive layer, resulting in improved structural repair performance.