Abstract: Complex ray tracing provides an efficient approach to dealing with the propagation and scattering of HF Gaussian-like beams, but the search for the ray path from source to observer is the most time-consuming part in the numerical implementation of the complex ray scheme. Based on the complex ray theory and the perturbation principle, an approximation method for the evaluation of beam fields in the paraxial region is developed, which simplifies the computation substantially, The theory and procedure of the method are presented and some application examples and numerical results are given.