The fine-structure splitting 1s22s22p 2P1/2-2P3/2 transitions in boronlike S11+ and Cl12+ were experimentally measured with a high precision spectrometer at the Shanghai high-temperature superconducting electron beam ion trap. The M1 transition wavelengths for S11+ and Cl12+ were determined to be 760.9635(29) and 574.1539(26) nm (in air), respectively. Compared to the previously observed results, the accuracies of current experimental results are improved by more than ten times and 200 times for S11+ and Cl12+, respectively. Additionally, the M1 transition energies in S11+ and Cl12+ were evaluated within the ab initio QED framework to compare with the experimental data. The present experimental results agree with the theoretical calculations and provide a possibility to test QED effects and correlation effects with high accuracy in few-electron highly charged ions.