Disclosed is an intelligent overflow buffer device. A hydraulic oil tank (1) is communicated with a reversing valve (2) through a hydraulic pump, a first operating oil port A of a control valve is communicated with one end of a rotary motor (3) through a first execution oil port C1, a fifth one-way valve (4.4), a third one-way valve (4.2), a first straight-link overflow valve (5) and a first one-way valve (4) are connected between the first operating oil port A of the control valve and a pipeline of the rotary motor in parallel, a one-way valve and a straight-link overflow valve are parallelly connected between a second operating oil port B of the control valve and the pipeline of the rotary motor through a second execution oil port C2, an electric proportional flow control valve (6) is connected between the four one-way valves, and a main oil pipeline connected between the one-way valves and the straight-link overflow valve in parallel is communicated with a hydraulic oil tank pipeline through an oil replenishing port T. Hydraulic impact of a rotary drilling rig during rotation is reduced, on-truck shaking of the rotary drilling rig during rotation is reduced, main-unit stability is improved, and service lives of relevant components are prolonged.