The invention discloses a digital relay protection device supporting a three-in-one network. The digital relay protection device comprises a multichannel Ethernet interface module supporting a three-in-one network interface; an Ethernet frame pretreatment IP (intellectual property) core module supporting SV sampling value, GOOSE, a station control layer and PTP (picture transfer protocol) message; a self-adaptive multichannel sampling value data synchronism module; and a data receiving and processing module for completing protection, measurement and control, metering, and joint locking functions of the relay protection device, and realizing the protection and automation functions of a smart substation. The digital relay protection device can be applied to the smart substation, and realizes the transceiving treatment of in-station data based on sampling value grouping or three-in-one network joint transmission, and provides a solution for realizing the function of the relay protection device of the smart substation under a uniform network frame; besides, the digital relay protection device can simplify an interface of the relay protection device and reduce the data processing ability, and improve the running stability and reliability of the relay protection device.