The present invention belongs to the integrated circuit electrostatic discharge (ESD) protection field and relates to an SCR device for an input/output port and power source clamping. The SCR device is used for simultaneously realizing input/output port protection and power source clamping. The SCR device of the present invention includes a main bleed-off device and an auxiliary control device; the auxiliary control device is adopted as a switch for controlling the main bleed-off device; when working normally, the auxiliary control device turns off the main bleed-off device, so that the normaloperation of a protected circuit is not affected; when an ESD event occurs, the auxiliary control device turns on the main bleed-off device, so that ESD current can be discharged; and the parametersof an internal RC path are designed, and therefore, the trigger voltage of the main bleed-off device can be reduced, and the trigger voltage can be modulated.