The invention discloses a one-way downhole circulating shut-in valve and a working method thereof. In the one-way downhole circulating shut-in valve, one end of an outer circulating cylinder is fixedly connected with an upper connector, and the other end of the outer circulating cylinder is fixedly connected with a lower connector; a differential-pressure mandrel is fixedly limited in the outer circulating cylinder; a pressure relief sheet which can crack under preset pressure is arranged on the upper connector; a valve holder is fixedly arranged at the lower end of the outer circulating cylinder; a valve plate and the valve holder are connected so as to be used for controlling a switch of the inner cavity of the outer circulating cylinder; an outer circulating hole is formed in the outer circulating cylinder; an inner circulating hole is formed in the differential-pressure mandrel. According to the one-way downhole circulating shut-in valve disclosed by the invention, through the control of annulus pressure, the isolation or the communication between the inside of an oil tube and the annulus is realized; the right hole of the oil tube is shut off upwards in one way so as to meet demands for well killing and leaking stoppage of a reservoir layer which is liable to leak, so that the economic loss caused by the complication of well killing, leaking stoppage and the like is reduced; the operation cycle of an oil test is shortened; the oil testing cost is reduced.