The paper discusses the problem of thermal state of three-way catalytic converter depending on engine load with spark ignition fueled with gasoline and natural gas. The measurements on the test bench were performed, during which the temperature of the exhaust gases in the exhaust system was measured with the help of thermocouples, and at the same time, the track of the thermal state of the catalytic converter was monitored using thermo-vision camera. The stable work of engine with different rotation speed and values of load was considered together with transient states. The results of the measurements were presented in forms of charts and selected thermograms, qualitatively presenting the issue of thermal state of the catalytic converter.