Inducing and manipulating magnetism in two-dimensional (2D) materials play a significant role in the development of next generation nanoscale spintronic devices. The influences of vacancy and strain on electronic and magnetic properties of monolayer buckled antimonene are investigated by first-principle calculations. It is found that antimonene transits from nonmagnetic semiconductor to magnetic half-metal due to the inclusion of vacancy. Its electronic and magnetic properties can be further modulated by applying in-plane biaxial strains. The ferromagnetic half-metal feature with 1 mu(B) magnetic moment is conserved within the strain range of 0-3%. When strain is above 4%, it will transform to an antiferromagnetic semiconductor without changing the total magnetic moment. On the other hand, small compressive strains could reduce the magnetism effectively and a nonmagnetic n-type doping semiconductive state is obtained when strain reaches -4%. A metastable ferromagnetic semiconductive state with enhanced magnetic moments of 3 mu(B) are found when the tensile strain exceeds 7%. In addition, the vacancy induced magnetic property is scarcely affected when antimonene is adhered on Sb2Te3 substrate. The tunable electronic structure and magnetic properties of monolayer antimonene may be utilized for the development of low-dimensional spintronics devices.