The invention provides a self-diagnosis detection circuit, device and method of a digital output channel, belongs to the technical field of industrial control, and aims at solving the problem that a technical scheme of simple and reliable self-diagnosis of the digital output channel lacks in the prior art. The circuit comprises an electromagnetic relay, and the electromagnetic relay is set to receive a digital control signal and output an electric signal converted by an electromagnet to an external circuit; the electromagnetic relay comprises two groups of output contacts, one group of contacts serves as dry contacts to form a dry contact output branch, and the other group of contacts is connected to an input signal control circuit to form a detection read-back branch. Thus, the simple and reliable pure-hardware detection circuit and method can be used, design of the self-diagnosis circuit of the digital output channel is simplified, and the circuit, device and method are suitable for self-diagnosis of wet-contact and dry-contact type digital output channels simultaneously.