Aiming at the limitations of experimental study on thermophysical properties of cryogenic PCMs，such as long duration，big deviation and harsh cold condition test，a highly accurate method to predict solid-liquid equi- librium (SLE) of PCMs，where SRK-UNIFAC model is used in the fugacity of PCMs in liquid phase and method of referenced state by hypothetic path is used in solid phase，was proposed． Based on the improved method，the thermophysical properties of composite cryogenic PCMs including eutectic composition，eutectic temperature and eutectic enthalpy were accurately predicted with a minor deviation． Furthermore，taking the LNG air separation unit as an example，the established simulating method with high accuracy to predict PCMs' thermophysical proper- ties was adopted for material selection and adaptive application for cryogenic energy storage unit in this project with high efficiency．