Tunable laser absorption spectroscopy (TLAS) technology has been widely used in gas detection.The quality of the second harmonic signal is closely related to the detection parameters. Therefore, it is very meaningful to analyze the optimization methods of detection parameters.This paper summarizes the selection rules of detection parameters according to the influence of the filter parameters in spectral line preprocessing,the sampling time of the system,and the time constant of the lock-in amplifier on the signal and the relationship between the parameters.The appropriate filter order and window width are selected according to the filtering principle and the root mean squared error (RMSE) value of the signal under different concentrations.The three evaluation indicators of signal-to-noise ratio (SNR),RMSE,and the ratio of amplitude in frequency domain of signal to noise (fSNR) are selected for time-frequency analysis to obtain the optimal sampling period value of 30 according to the trend of curves.The optimal sampling time can be calculated according to the specific parameters of the experimental system.The appropriate time constant is selected according to the relationship between the main frequency band of the signal and the cut-off frequency and the filtering effect.The quality of the second harmonic signal can be improved by comprehensive analyzing the three detection parameters and summarizing the selection method.The parameter selection method proposed in this paper is of great significance to improve the accuracy of the second harmonic in practical applications.