The invention discloses a method and a device for evaluating contribution degree of a power distribution network project to power supply reliability. The method does not depend on an accurate topological structure of the power distribution network; only the power supply area of the feeder line group needs to be collected; the wiring mode and the distribution automation configuration condition arerealized; according to the change amplitude of the first power distribution network power supply reliability index before project implementation and the second power distribution network power supplyreliability index after project implementation, the contribution degree of the power distribution network project to the power supply reliability is calculated through a contribution degree calculation formula; thus, the contribution degree of the power distribution network project to the power supply reliability can be approximately evaluated, and the technical problem that an existing power distribution network project contribution degree calculation method for the power supply reliability can only calculate and analyze the contribution degree of the power supply reliability of the power distribution network with the accurate topological structure is solved.