Two-dimensional ferromagnetic topological semi-metals have attracted much interest owing to their fascinating spintronic applications. Using first-principles calculations, we propose a stable transition metal nitrogen halide compound, namely, VNI monolayer, to display intrinsic ferromagnetism with high Curie temperature T_C (∼510 K) and strong out-of-plane magnetism. It is found to be a topological Weyl nodal line material, which can be fully spin-polarized by controlling the on-site Coulomb interaction. Its nodal line can be destroyed by orienting the magnetization axis. Additionally, biaxial strain enables efficient tuning of the magnetic properties by switching the easy magnetic axis from an out-of-plane to in-plane direction with an enhanced T_C to 540 K. These results highlight the great application potential of a VNI monolayer in low-dimensional topological magnets.