Abstract: Based on two physical phenomena,laser induced fluorescence (LIF) and depolarization, resulting from elastic scattering on nonspherical particles, a compact lidar system for realtime standoff detection of bioagents/bioaerosol is developed. The system includes three laser sources, two receiving telescopes, depolarization component and spectral signature analyzing spectrograph. For the horizontal polarization measurements, it can be concluded that,1) the depolarization ratios are wavelengthdependent; 2) the discrimination efficiency increases significantly with the number of wavelengths used. And from the depolarization timespace distributions results, it can be revealed that, the aerosol depolarization ratio remains at a low level within the boundary layer, and can be affected by the wind, humidity, temperature and other meteorological factors, the complex zigzag vertical distributions of depolarization ratio is obvious in the tropospheric layer, the depolarization can reach 0.3 at some clouds. Finally, the Mie scattering observation results with the 532 nm and 355 nm wavelengths show that the more complicated layered structure of aerosol timespace distribution can be obtained with the 355 nm wavelength if the output energy of two wavelengths are at the same level.