Abstract: A new model for sky-wave over the horizon radar(OHTR) ionospheric channels based on ray tracing and phase screen/diffraction method is developed.The international reference ionosphere model and the international geomagnetic reference field（IGRF)model are integrated with a classical 3D ray tracing code A new algorithm for matching of outbound and return ray paths is developed to meet the need of sky-wave two-way channel modeling.The two-frequency，two-position，two-time mutual coherence function of ionospheric channel is calculated directly by phase screen/diffraction method，from which a stochastic pulse response function for strong scintillations is obtained.Then the stochastic pulse response function is modified to be suitable for weak scintillations.After that，the sky-wave OTHR two way channel model is calculated by convoluting the pulse response function corresponding to matched outbound and return ray paths in two domains，and including the channel loss.This channel model can be used for sky-wave OTHR signal modeling and signal processing studies.