Abstract: This paper introduced the process flow and transformation items of 1.8 Mt/a FCC gasoline hydrodesulfurization unit which used Axens company Prime-G⁺ technology to transform according to the national standard of grade Ⅴ gasoline. Initial operation under full capacity and preliminary optimization condition were analyzed. The problems existing in the start-up process were analyzed and solutions were put forward. The results showed that the Prime-G⁺ process was mature and reliable, and the indexes of light, heavy and blended refined gasoline were up to the requirements of the national standard of grade Ⅴ gasoline. The octane number loss could be reduced by reducing the desulfurization rate of first stage and second stage HDS, and the measures could be further optimized.