Owing to the novel structure and rich electromagnetic properties, graphene shows very great promise in developing future nano-electronic devices and has thus attracted ever-increasing attention. Its isomorph-single layer, hexagonal boron-nitride (h-BN), in which carbon atoms in graphene are replaced with alternating boron and nitrogen atoms in the sp2 lattice structure, has led to a new research boom in condensed matter physics and material science. Although an h-BN layer has a similar structure to graphene, it possesses a number of properties different from its carbon counterpart. In this work, the first-principles method based on density functional theory is used to study the structural stability, magneto-electronic properties and mechano-magnetic coupling effects for an armchair BN nanoribbon doped with different transition metals (ABNNR-TM). The calculated binding energy and molecular dynamic stimulation suggest that these structures are stable. Meanwhile, the calculated results show that ABNNR-TM holds diverse magneto-electronic properties upon different TM doping. For example, they may be nonmagnetic metals, nonmagnetic semiconductors, magnetic metals, magnetic semiconductors, or bipolar magnetic semiconductors. In particular, the bipolar magnetic semiconductor is an important semiconducting material, which has promising applications in the fields of the giant magnetoresistance and the spin rectifying devices. Besides, the investigations on mechano-magnetic coupling effects indicate that magneto-electronic properties of ABNNR-TM are very sensitive to the stress, which can realize the phase transformation between the nonmagnetic metal, nonmagnetic semiconductor, magnetic metal, magnetic semiconductor, bipolar magnetic semiconductors, and half metal. Particularly, the obtained wide-gap half metal is of significance for developing novel spintronic devices. In short, this work demonstrates that it is possible to tune magneto-electronic properties of ABNNR-TM by mechanic method.