Abstract: Because the accuracy in estimating complex system parameters is difficult to ensure by adopting traditional calculation methods,an improved intelligent optimization algorithm was introduced in this article.The new optimization algorithm adopted a new method which was based on the cloud model theory to construct the probability model of the problems' solution space.The test by some benchmark functions shows that the new algorithm can effectively improve the convergence speed and searching precision.And this method is applied to calculate binary interaction parameters k_ij in PC-SAFT state equation of the supercritical ethylene coordination polymerization system.A comparison with literature data shows that calculated binary interaction parameters can accurately describe the gas-liquid phase equilibrium among components.