Background: Isophthalic acid (IPA) is commercially produced using the Co-Mn-Br catalyst system, which suffers from the shortcomings of the discharge of CH 3 Br and corrosion of equipment. It is necessary to develop a technology to avoid the pollution caused by bromide. The production of IPA from the oxidation of m-xylene (MX) by air is realized under catalysis with H 3 PW 12 O 40 (HPW) loaded on carbon and cobalt. Results: Tartaric acid has been used to improve the catalytic activity of the HPW@C catalyst. Experiments indicate that the best modification condition is calcining the carbon at 450°C for 4 h after being soaked in a 2.0 mol L −1 tartaric acid solution for 10 h. Surface characterization reveals that the tartaric acid modification leads to an increase in the acid groups and a reduction in the basic groups on the carbon surface. Conclusions: The MX conversion obtained using the HPW@C catalyst prepared from modified carbon is 6.77% over that obtained using the HPW@C catalyst prepared from the original carbon. The IPA generated using the former is 71.1% over that generated using the latter. The catalytic activity of the HPW@C catalyst relies on its surface chemical characteristics and physical properties. The surface chemistry plays a more important role than the physical properties.