A TLAS technigue was used to measure the concentrations of the exhaust gas components. To this end， selecting NO gas as a target gas for laboratory static test and using an IC laser as a detector light source， a direct detection method and harmonic detection method were used to measure four different concentrations of a standard NO gas， and the test results were consistent with the real concentrations of the standard gas. When using the direct detection method， the root-mean-square of the relative error was 5.4%， with a maximum absolute error of 18.6×10-6， and the theoretical resolution of 2×10-6， while for the harmonic detection method， the root-mean-square of the relative error was 1.4% with a maximum absolute error of 13×10-6， and theoretical resolution of 10-7. In data processing， the temperature correction was used to achieve accurate measurements at temperature fluctuation. At the same time， the standard gas concentrations with different velocity were measured on line， which indicated that the gas flowability had no effect on the test results. Study shows that the TLAS method has good dynamic response， and environmental adaptability， so that it can be used in real-time correction for transient environmental conditions in order to achieve high precision and sensitivity of transient measurements in a complex test environment.