The invention discloses a method for automatically correcting accuracy of a protection and monitoring device. The method comprises the following steps: configuring voltage and current types of each channel of AC plug-in and reference values thereof, generating a configuration file and unloading the configuration file into the protection and monitoring device; applying analog quantities corresponding to the reference values to various channels used by the protection and monitoring device by a relay protection testing device after the protection and monitoring device is started; executing an automatic accuracy correction command by an operator according to a menu of the protection and monitoring device, performing accuracy correction calculation on CPU in the protection and monitoring device, and storing the calculated accuracy coefficient of each channel. The voltage/current quantity is applied to the AC plug-in of the protection and monitoring device by adopting the relay protection testing device, the automatic accuracy correction method is realized by using the protection and monitoring device, and a process of enabling the device manufacturer to participate in correction is eliminated, so that an operator in an engineering field can conveniently and efficiently complete the accuracy correction of the AC plug-in.