A Rayleigh-Mie lidar used for detecting atmosphere temperature and aerosol is designed. The signal-to-noise ratio of the atmospheric backscattering signal was simulated numerically. Effects of the laser pulse energy, number of laser pulses, telescope aperture, resolution of the spatial distance, and narrow-band interference filter bandwidth and transmittance on the lidar signal-to-noise ratio were discussed. According to the simulation results, when the lidar runs during the daytime, the maximum detection height of aerosol is up to 10.6 km with the Mie scattering signal using a interference filter bandwidth of 1 nm. The maximum detection height of middle atmospheric temperature is up to 47.1 km with the Rayleigh scattering signal using a interference filter bandwidth of 0.2 nm.