It aims to search for a proper calculation method of radio interference and audible noise to AC/DC hybrid lines arranged on the same tower. First, the characteristics of surface field strength were analyzed theoretically; second, the synthesized field strength was calculated with linear superposition theorem; then the principle, which contains radio interference and audible noise of hybrid lines should be computed in the same weather, was proposed in this paper combined with influence of humidity to corona. The results of three calculation methods were compared and calculated in a sunny and a rainy day. And it indicates the BPA correction formula is an effective method to calculate radio interference and audible noise of AC/DC hybrid lines at present.