The invention relates to a backflow-prevention disposable drainage bag. The disposable drainage bag comprises a drainage pipe connector mechanism, a drainage pipe, a stop clip, a hanging tube, a hanging belt, an anti-reflux plate, a liquid storage bag and a draining device, wherein a liquid inlet and a liquid outlet are formed in the liquid storage bag; the drainage tube penetrates the liquid inlet and is fixed on the top of the liquid storage bag; the stop clip is fixed on the drainage tube; the drainage tube connector mechanism is fixed at the outer end of the drainage tube; the draining device penetrates the liquid outlet and is fixed at the bottom of the liquid storage bag; the hanging tube and the hanging belt are detachably fixed on the top of the liquid storage bag; the anti-reflux plate comprises a first reflux layer and a second reflux layer, the first reflux layer is fixed on the second reflux layer, and the first reflux layer and the second reflux layer are flakes which have a conical structure and are made of a latex material. By adopting the ackflow-prevention disposable drainage bag, liquid backflow can be effectively prevented; and the connection structure of the drainage tube is improved, so that the connection is convenient and rapid, the operation is simple, slippage or leakage cannot happen, and health safety of users can be overall protected.