Temperature and humidity Raman lidar can detect atmospheric temperature and humidity with high spatiotemporal resolution and high accuracy. Based on the principles of atmospheric Raman scattering lidar, a comprehensive simulation model encompassing laser emission system, atmospheric target characteristics, optical transmission properties, and optical reception and detection systems was constructed in this work. Then the four-channel detection signals of Raman lidar was simulated and inverted, and the simulation results were compared with the actual measurements. The comparison results demonstrated that the determination coefficients of temperature and humidity are 0.999 and 0.907 respectively, validating the accuracy of the simulation model. On this basis, the simulation model was further employed to optimize the parameters of the Raman lidar system. By iterating the parameters of the emission and detection modules, the wavelength of 355 nm was determined as the center wavelength of the excitation light of the lidar system, and 353.5 nm and 354 nm were selected as the center wavelengths of the rotating Raman filters to improve the detection sensitivity and accuracy.