The solar background radiation seriously affects the detection performance of Raman lidar during daytime. In order to improve the detection height and accuracy of Raman lidar during daytime, a Raman lidar system with laser wavelength of 354.8 nm was designed. The influence of 354.8 nm and 532 nm laser sources on the detection performance of Raman lidar was discussed. The optical path design of the system was completed. The combination of photoswitch and monostatic telescope reduced the receiving field of view angle and optimized daytime detection performance. The photoswitch was composed of polarization splitting prism and 1/4 wave plate. With the minimum statistical temperature uncertainty as the standard, the parameters of rotational Raman channel interference filter were selected through simulation analysis. And the detection performance of the system was simulated. During simulation, the laser energy was 200 mJ, the frequency was 50 Hz, the integration time was 20 min, and the range resolution was 105 m. Under the condition of depolarization, the statistical temperature uncertainty of the monostatic Raman lidar system less than 1 K was obtained up to 3180 m height in the daytime. The statistical error of water vapor mixing ratio was less than 0.001 g/kg up to 2400 m height during daytime. The simulation results show that the performance of daytime detection has been improved to some extent.