At present,high precision detection of the concentration of many types of gases can be achievedbased on the tunable semiconductor laser absorption spectroscopy(TDLAS)technology.However,in actual engineering applications and mass production of instruments,the performance of some lasers themselves and the limitations of the volume of the detection instrument(larger reflector cells cannot be used),as well as the influence of environmental factors,make it difficult to distinguish low concentration gases or affect the detection accuracy.To improve this problem,a calculation method using a fixed wave gate and a difference is mainly introduced to achieve effective resolution of low concentration carbon monoxide,and low concentration carbon monoxide are measuredunder different temperature conditions.The test results show that the error of detecting 10.01 ppm CO is 2.2%under constant temperature conditions,and the maximum detection error is 1.72 ppm within the temperature difference range of 12℃.Under different environmental conditions,the processing method is able to effectively carry out the detection of low concentration carbon monoxide,and the test results can satisfy the requirements of the actual use of the project,offsetting the impact of device performance to a certain extent.This paper has a positive effect on instrument development,design and production when the batch is large or there are large individual differences in the devices.