A 780-nm high spectral resolution lidar was designed herein based on a laser diode. A distributed feedback semiconductor laser was used as the seed of the light source system. A tapered semiconductor optical amplifier driven by pulse current was used to output the narrow line width pulse laser. The optical splitting system mainly comprised a narrow-band interference filter, a Fabry-Perot etalon, and a ⁸⁷Rb absorption cell. The bandwidth of the narrow-band interference filter was 0.5 nm. The full width at half maximum of the Fabry-Perot etalon was 2.8 GHz. Solar background light was filtered by their combination. The Mie scattering signal was absorbed by the ⁸⁷Rb cell at the temperature of 338 K, which had an inhibition rate of up to 33 dB. The Rayleigh scattering signal was then effectively extracted. Based on the American standard atmospheric model, the detection capability of the high spectral resolution lidar was verified via numerical simulations. This research was highly significant to the detection of aerosol optical parameters.