The invention discloses an AC/DC dynamic interaction idle work influence scope evaluation method comprising the following steps: 1, simulating calculating a minimum commutation bus voltage value; 2, determining an influence scope on an AC system by AC/DC interaction idle work; 3, evaluating performance. The evaluation combines precise calculation of a jacobian expanding matrix and direct effectiveness of an electromagnetic transient program PSCAD/EMTDC and RTDS, thus fast and accurately determine the influence scope against the AC network by DC system idle work impact; the simple and efficient method can evaluate the dynamic interaction idle work influence scope in the real AC/DC interconnected network, so system operation people can handle and evaluate the influences against the AC system by the DC idle work impact, thus directionally improving AC network voltage support capability, reducing a voltage offset normal value area caused in a DC system fault process, reducing influences against power system loads, and ensuring the AC/DC interconnection network to stably and safely work.