Based on the METIS integrated modeling platform, combined with the experimental data of the #34512 shot detached divertor operation on the HL-2A, this paper selects suitable physical models, and compares and analyzes the integrated modeling results with the experimental results. The modeling results are in good agreement with the experimental results. On this basis, the reason for the decrease of the peak heat fux on the divertor targets is investigated using the METIS simulator. The results show that the two factors of entering the H-mode and the radiation enhancement efect generated by impurity injection work together to reduce the heat fow on the targets. Finally, the diferent efects of N, Ar and Ne impurity gases on the heat fux reduction of the targets are simulated under the condition that the plasma line-average efective charge (Zef) is kept unchanged. The results show that N and Ar are both better than Ne in controlling the heat fow on the targets, and N has the best compatibility in the core, which can not only reduce the boundary heat fow but also maintain the core confnement performance.