Ice crystal particles form complex mixed-state features during the melting process, which in turn affects their optical and radiative properties, with important implications for studies of global radiation effects and weather forecasting. Early researchers assumed the shape of ice crystal particles as spherical for theoretical studies. Recently, various standard nonspherical particle models such as hexagonal, cylindrical, and bullet have been developed to study the optical properties of ice crystal particles. However, the real ice crystal particle morphology is much more complex than the standard models. For example, the melting process of ice crystal particles is a very common but extremely important process, which is important for the study of microphysical and optical properties of ice crystal particles. During rainfall process, ice crystal particles are transformed into raindrops in the melting layer, and the microphysical properties such as the morphology and mixing state of ice crystal particles undergo a complex change. For the study of the melting process of ice crystal particles, there are advantages and shortcomings in both field observations and radar observations. Therefore, it is important to construct an accurate melting ice crystal particle model to study the optical properties of ice crystal particles during the melting process.In this paper, a non-spherical non-uniform model is proposed to simulate the morphology and mixing state of ice crystal particles during the melting process, and the Discrete Dipole Approximation (DDA) method is used to systematically study the effect of frequency, aspect ratio, and Ice-to-Water Mixing Ratio (IWMR) on the optical properties of melting ice crystal particles.The results show that the optical properties (extinction efficiency factor, scattering efficiency factor, asymmetry factor, and scattering phase matrix) of ice crystal particles at different melting stages have large differences. Specifically, the larger the particle size of melting ice crystal particles, the larger the oscillation amplitude of its extinction efficiency factor, scattering efficiency factor and asymmetry factor with frequency change, and the larger the oscillation of the scattering phase matrix element of melting ice crystal particles, with the increase of frequency. With the melting of the ice crystal particles, these optical parameters show regular changes with the decrease of IWMR, which also implies that ignoring the melting process of the ice crystal particles may lead to misestimation of their optical properties. The results also show that the influence of ice crystal particle morphology on extinction efficiency factor, scattering efficiency factor and asymmetry factor is mainly in the lower melting stage. When the melting degree is low, the aspect ratio of the ice crystal nuclei has a significant effect on all the optical property parameters. When the melting degree is high, the effect of the nuclear aspect ratio on the non-scattering optical parameters such as the particle extinction efficiency, scattering efficiency and asymmetry factor is basically negligible, but with the increase of the particle size, the nuclear aspect ratio of the ice crystals still has a significant effect on the particle scattering matrix elements. The results of the study can provide a reference for further understanding of the evolution law of microphysical properties of ice clouds and improving the accuracy of ice-water content inversion and other studies.This paper presents a parameterized model of melting ice crystals, which is based on the actual scenario of the complex evolution process of particle morphology and mixing state exhibited during the melting process of ice crystal particles. This model has been developed in order to address the practical needs of microwave remote sensing and inversion algorithm research of ice crystal particles. A particle model is constructed and the DDA method is employed to conduct a comprehensive investigation into the influence of various factors, including particle size, frequency, morphology and melting degree, on the optical characteristics of ice crystal particles. These characteristics include extinction efficiency factor, scattering efficiency factor, asymmetry factor and scattering matrix elements.