The embodiment of the invention provides a preliminary plan determining method and apparatus of a power grid accident. The method comprises: a grid accident signal is monitored and a fault device and a fault device title are determined according to the grid accident signal; on the basis of the fault device title, searching is carried out on a preset accident preliminary plan model to obtain standby preliminary plans, wherein the accident preliminary plan model contains titles of all fault devices and preliminary plans corresponding to the titles of all fault devices; checking is carried out on all standby preliminary plans according to a preset checking rule to obtain a checked preliminary plan, wherein the operating way of the device corresponding to the checked preliminary plan is identical with the operating way of the fault device after isolation, and the checked preliminary plan is used as a formal preliminary grid accident plan of the fault device. Therefore, a needed preliminary plan can be searched rapidly and accurately. Meanwhile, the searched preliminary plan is checked, so that a problem that the searched preliminary plan is not suitable for the accident because of the large change of the grid topological structure can be solved; and thus safety of the power grid is improved.