The utility model provides a no-bus compact type relay protecting device which has advantages of small volume and high IP protecting grade and is suitable for outdoor mounting and use. The no-bus compact type relay protecting device comprises a housing which can be directly suspended on an outdoor hanging rod, a holding rod or wall. The profile of the housing is a cuboid. The housing with a closed structure is internally provided with three circuit boards which are separately arranged and are connected through hard terminals, namely a master control circuit board which generates an instruction for controlling action of a relay, an IO circuit board for transmitting various signals, and an AC circuit board which is connected with an external electric network. The hard terminals comprise a first hard terminal which is used for connecting the AC circuit board with the IO circuit board and is provided with 36 pins, and a second hard terminal which is used for connecting the master control circuit board with the IO circuit board and is provided with 77 pins. The AC circuit board converts the high voltage and large current of the external electric network to a low-voltage analog voltage signal for being transmitted to the IO circuit board. The IO circuit board transmits the received low-voltage analog voltage signal to the master control circuit board, and simultaneously the IO circuit board transmits a switch signal which controls action of the relay to an external relay.