A wavelength tunable lidar is designed based on OPO laser. The output wavelength of the lidar can be tunable continuously in the range of 192~2750 nm. The optical splitting system of the lidar is composed of rotatable gratings and circular apertures. By adjusting the diffraction angle of the rotatable gratings, the lidar can receive the return signal at the specific wavelength. The photomultiplier tube and InGaAs detectors are used to transform the optical signal into electric signal in the corresponding wavebands. Subsequent data acquisition and processing are performed by data acquisition system and PC. Numerical simulations are performed with the standard atmospheric model. The detection ability of the lidar in the different wavebands is verified by the simulation results. The lidar is of important significance for fine detection of microphysical properties of near-surface aerosols.