Abstract: Both the improved Monte Carlo method and the adaptive ray sub-division method are proposed to solve the bottle-neck problem of computation resource and efficiency resulting from the great number of rays for the ray-tracing method to calculate the electromagnetic (EM) scattering of multi-layered dielectric structure.The improved Monte Carlo method regards ray splitting as reflection or refraction separately based on special probability calculated by the energy distribution of the reflected and refracted rays, and the ray number keeps the same.The adaptive ray subdivision method reduces the number of rays farthest by choosing sparse initial rays, and ensures the calculation accuracy by adaptively adding rays based on the variety of structure and material.Simulation experiments and reference results show that the proposed two methods are accurate and efficient.Finally, the paper analyses the merits and demerits, and points out the scope of application and suggestions in practical aspect.