The invention relates to a relay protection method and device of a power distribution network containing a distributed power supply. The relay protection method comprises the following steps of carrying out equivalence on the distributed power supply and a load at an access point of the distributed power supply to acquire an equivalent circuit of a downstream circuit of a protected circuit; calculating a main protective current setting value of the protected circuit according to the equivalent circuit, and setting the main protective current setting value as an action current value of an overcurrent protection device of the protected circuit; calculating a backup protection current setting value of a downstream section adjacent to the access point of the distributed power supply; and setting the action current value of the overcurrent protection device of an upstream section adjacent to the access point of the distributed power supply as the backup protection current setting value after prolonging a predetermined time interval when the overcurrent protection device of the downstream section adjacent to the access point of the distributed power supply does not act. By the relay protection method, a perfect communication network is not needed, the influence of the distribution power supply on relay protection is eliminated, and the relay protection circuit setting value can be automatically adaptive to an access situation of the distributed power supply. The relay protection method is simple and practical and is simple in calculation.