Generating a single material with multiple ferroic properties 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 distributed defects in the materials. Here, the strong influence of oxygen vacancies (V-O) on the magnetic properties of YMnO3 is demonstrated. The first-principles calculations reveal that the V-O at axial positions can induce a nonzero net magnetization along the c-axis. By structural characterization and magnetic measurement, this theoretically predicted ferromagnetic property is experimentally confirmed in the YMnO3 film grown on a c-Al2O3 substrate. The large in-plane compressive strain provided by the Al2O3 substrate allows to create the axial V-O of YMnO3 film in this system. The ferroelectricity of YMnO3 is also preserved even under large in-plane compressive strain. Therefore, the coexistence of the ferroelectric and ferromagnetic properties can be realized in the YMnO3 film, which is of practical interest for technological applications.