Abstract: Frequency selection is a necessary means to improve HF communication quality, but it is difficult for HF mobile users to obtain the location information needed for frequency selection link calculation. The algorithm of using multiple station signals to recognize the position of a mobile terminal at any time is designed. The algorithm reversely applies the time difference of arrival (TDOA) location theory. The signal delay difference of two sites is proportional to the difference of virtual path, three sites form two hyperbola curves, the curves intersect at the position of the mobile terminal. The key of the algorithm is to use the national radio observation network signal, and a position probability function based on the time difference error of the prediction vale and the measured data is designed. Simulation results and measured data shows the feasibility of the algorithm. Improvements of the algorithm strategy is discussed, it is expected to realize engineering application as soon as possible.