In order to solve the problem of line selection in the analysis of hydrogen laser leakage detection spectral signal， a simulation model of direct absorption concentration inversion process of hydrogen laser absorption spectrum was established， and the reconstruction accuracy of spectral lines of three different linear functions was studied by combining Hitran database， and the influence of pressure change on the absorption coefficients of hydrogen absorption spectra under three linear functions was studied. The results showed that the reconstruction accuracy of the Gauss linear function was the highest among the three linear functions， and its reconstruction error was less than 0.02%. The maximum reconstruction error of Voigt linear function and Lorentz linear function were 0.37% and 2.58%， respectively， which could verify the accuracy and reliability of the simulation algorithm. The simulation results showed that the peak absorption coefficients of the three types of lines increase with the increased of pressure. In the range of 0.1~5.0 atm， the peak absorption coefficient of Lorentz linear was the largest， and the simulated peak absorption coefficient of Lorentz linear was the minimum 1.38 times and the maximum 17.77 times of Gauss linear. The minimum value was 2.07 times that of Voigt and the maximum value was 18.41 times that of Voigt. This study has laid a scientific basis for further research on hydrogen laser absorption spectrum detection， thus providing theoretical guidance and reference for practical application.