A method for determining interference from a NGSO satellite earth detection system to a deep space detection system is disclosed. The method comprises the following steps: pinpointing locus parameters of two time varying systems; unifying a reference system of the two time varying systems; pinpointing satellite system performance parameters of both sides; determining a time arc segment concerned by interference analysis; determining total time of the interference analysis and a sampling frequency; acquiring space position information of each sampling time corresponding to the two time varying systems in the interference time arc segment respectively and acquiring sending and receiving gain at a direction of a interference link and a interference link distance length; calculating a power spectrum density when each sampling time interference signal arrives at a disturbed link receiving system; determining same frequency interference by combining an international interference protection standard. By using the method of the invention, the interference generated by the NGSO satellite earth detection system on the deep space detection system in a corresponding frequency range can be accurately determined. An antijamming capability of the deep space detection system can be increased and a project is easy to be realized.