At present, the technology for the performance evaluation of gas leak thermal imaging detectors is not sufficiently well-developed, and there is no systematic research report on the test systems or methods of the corresponding evaluation index. However, it is difficult for the performance evaluation methods of conventional thermal imaging cameras to directly evaluate the detection capabilities of gas leak thermal imaging systems. We designed a test and evaluation system that can measure the performance of gas leak thermal imaging systems with multiple types of performance indicators. NECL, MRGC, and MDGC were measured experimentally in a laboratory environment with ethylene and methane gas as the detection target. The experimental measurements verify that the test evaluation system is feasible and practical.