To search for proper alternatives to improve the magnetic properties of Nd₂Fe₁₄B, using first-principles density functional theory calculations we have systematically studied the R₂M₁₄B (R = lanthanides from La to Lu; M = Mn, Fe, Co, and Ni) compounds with the isomorphic structure of Nd₂Fe₁₄B. The results show that for rare-earth elements, Pr is the most suitable choice for considering as an alternative of Nd. As for the substitution of Fe in Nd₂Fe₁₄B by other transition-metal elements, Co is much more suitable than Mn and Ni because the latter two result in too significant reduction of the magnetic moment.