Orientation-averaged lidar linear depolarization ratios (LLDR) of spheroid dust aerosols are carried out based on discrete dipole approximation (DDA) for size parameters from 0.1 to 23 (corresponding to effective radius from 0.01 to 2 μm at wavelength of 550 nm).The effects of the asphericity degree on the LLDRs for both monodisperse and polydisperse dust aerosols are performed by comparing LLDRs at different spheroid aspect ratios.For monodisperse spheroid,the dust LLDRs show strong dependences on aspect ratio and size parameter.For prolate spheroid dust particles,small LLDR values are found in the Rayleigh domain as opposed to large values in the Mie domain.Nevertheless,for oblate spheroid,large LLDR dust particles in the Mie domain can produce small LLDR values.For example,the dust LLDR has a value of about 0.1% at spheroid aspect ratio of 1/16 when the size parameter reaches 3.For monodisperse dust particles,the aspherical degree increases their LLDRs only at size parameters smaller than 0.5.However,for polydisperse aerosols,the degree of dust asphericity enhances their LLDRs.