Resistive switching is observed in single SnO2 nanowire device with two back-to-back Schottky diodes. The underlying mechanism can be interpreted well by the switchable diode effect, which is caused by tunable Schottky barrier height due to the drift of charged defects induced by external electrical field. A resistance window of more than 3 orders of magnitude has been achieved. The device also shows an excellent performance of endurance and retention time. Additionally, a very small current under negative bias is observed, which can avoid the sneaking current induced in the nearby devices. Due to the greatly reduced device size, power consumption and inherent nature of Schottky diode, the work shows here should be useful for the development of high density circuitries.