Simultaneously achieving more than one ferroic properties in a single material has been the hotspot of research interest for decades.The existing studies mostly focus on the intrinsic properties of multiferroic materials,overlooking the importance of the widely distributing defects in the materials.Here,we demonstrate the strong influence of oxygen vacancies (VO) on the structural and magnetic properties of YMnO3.Our first-principles calculations reveal that the in-plane VO are likely to form and induce Mn ions to deviate from 1/3 positions,while VO at axial positions can induce a non-zero net magnetization along the c-axis.We also demonstrate that by large in-plane compressive strain,the axial VO of YMnO3 can be easier to created.Therefore,the coexistence of the ferroelectric and ferromagnetic properties can be realized in the YMnO3 film grown on certain substrate,which is of practical interest for technological applications.