The invention relates to an electric power system partition power supply capability determination method. The method comprises the following steps of determining basic information of electric power system partitions and constructing trend and stable data required by calculation; inspecting data rationality, and adjusting correlation parameters of trend distribution, a voltage level, generator output and the like in the partitions; calculating dynamic components included in the partitions and determining response conditions of the dynamic components after a system is disturbed; analyzing a specific condition of a power grid and selecting a load node increase mode; determining a system constraint condition during calculation, selecting a correlation fault influencing a partition power supply capability, and calculating the partition power supply capability under each type of faults; analyzing a factor influencing the partition power supply capability and researching a weak link of the power grid; and determining a maximum power supply capability of the power grid partitions and assessing power grid safety. In the technical scheme of the invention, the weak link influencing the partition power supply capability can be discovered, the maximum power supply capability of the partitions is determined and a good support is provided for power grid operation safety and planning and decision making.