The invention provides a method and a device for evaluating the power supply capacity of a power distribution network containing new energy. The method comprises the following steps: calculating nodevoltage according to active power increment and reactive power increment of accessible new energy of a power distribution network; judging whether the node voltage is out of limit or not; if yes, determining the power supply capacity of the power distribution network containing the new energy according to the active power of the power distribution network capable of accessing the new energy; otherwise, increasing the active power of the power distribution network capable of accessing the new energy, recalculating the node voltage until the node voltage exceeds the limit, and determining the power supply capability of the power distribution network containing the new energy according to the increased active power of the power distribution network capable of accessing the new energy. The relation between the power increment of the power distribution network accessible new energy and the node voltage increment is considered, the accuracy of the evaluation result does not depend on the reasonability of the load distribution coefficient, the evaluation result is accurate, the evaluation process is simple, only simple mathematical calculation is needed, and the method has the advantagesof being simple in calculation process and small in calculation amount.