The phase state information of cloud water is important for the airborne measurement of the microphysical properties of a cloud. A cloud particle detection system based on polarization detection, which can be used to detect the size and phase state of cloud particles for particle diameters of less than 50 µm, was developed by detecting the energy of the forward scattering and the depolarization of backscattered light. The sensitive area was calculated through the width and depth of the field of view of the laser beam. The system was calibrated using standard particles. The response curve of the system to the cloud particles was obtained by calculating the relationship between the standard particles and the cloud droplets. Finally, the liquid droplets and typical nonspherical particles were measured, and the results compared with a simulation. The comparison results indicated that the system could detect spherical and nonspherical cloud particles and could discriminate between nonspherical cloud particles and liquid droplets.