Mn3+x Ga1-x N compounds with x = 0.0 and 0.1 were prepared by re-sintering Mn2N0.86, Ga bulk and Mn powders. These compounds are deduced to be the N-deficiency ones. In Mn3GaN, a step-like magnetic transition, from frustrated antiferromagnetism to paramagnetism with increasing temperature, occurs at 370 K, while the same magnetic transition of Mn3.1Ga0.9N is far above 380 K. The enhanced magnetization of Mn3GaN at low temperatures is ascribed to the fast lowering of antiferromagnetism. The electrical resistivity of Mn3GaN exhibits a typically metallic conducting behavior with a positive magnetoresistance of 4-7%.