Steady unipolar resistive switching of Pt/YMn(1-delta)O(3)/Pt MIM structure is investigated. High resistance ratio (>10(4)) of high resistance state (HRS) over low resistance state (LRS) and long retention (>10(5) s) are achieved. It is suggested that the Joule heating and Poole-Frenkel effect dominate respectively the conduction of the LRS and HRS in high electric field region. The resistive switching is explained by the rupture and formation of conductive filaments in association with the local Joule-heat-induced redox inside YMn(1-delta)O(3).