The invention discloses a device and method for automatic sand flushing of a water engineering small gate dam based on the internet of things technology. The device includes a sensing system, a dispatching information system, a camera system, a host computer, and an information execution system, wherein the sensing system, the dispatching information system, the camera system, the host computer, and the information execution system are mounted at a certain elevation near the gate dam in an upstream reservoir area; the sensing system includes sensor transmitter, a sensor receiver, an A/D digital-to-analog conversion card, an amplifying circuit; and the sensing system, the dispatching information system, the camera system, a mobile device, a gate hoist and the like are organically connectedby the internet of things technology. silt elevation in a reservoir is automatic sensed, water level elevation in the reservoir area is automatic read, the demand for reservoir dispatching informationis received, after comprehensive analysis, the opening and closing of a sand flushing hole gate are controlled to realize automatic sensing and automatic drainage of the silt in the reservoir as wellas intelligent control of reservoir dispatching.