Cirrus clouds, typically found at altitudes above 6 km, consist of non-spherical ice crystals and play a crucial role in the earth's radiation balance. Previous in-situ observation experiments have revealed a significant presence of hollow ice crystals in cirrus clouds. However, due to the absence of appropriate forward model, the existence of these hollow ice crystals is often overlooked in lidar observation studies. Based on prior in-situ observations, this paper establishes an empirical relationship between the hollowness and the length of hollow ice crystals, addressing the limitations of the fixed hollowness assumption used in previous hollow ice crystal models. The derivation of the physical optics approximation method based on beam-splitting and the calculation process for the backscattering properties of hollow ice crystals are introduced in detail. The simulation results show that both the wavelength depolarization ratio and the color ratio of ice crystals at 532 nm and 1064 nm are dependent on crystal size, and especially, the color ratio of ice crystal dooecreases monotonically with the increase of crystal size.