It is highly attractive but challenging to develop earth-abundant electrocatalysts for nitrogen (N 2 ) fixation. Here, by using density functional theory (DFT), we systematically investigate various single transition metal atom (Ti, V, Cr, Mn, Fe, Co, Ni, Ru, Rh and Pd) modified MoP surfaces as potential N 2 reduction electrocatalysts for ammonia (NH 3 ) synthesis. Through comparison of the stabilities of metal atom modified MoP, the adsorption energies and the bond lengths of N 2 on different atom modified MoP, we select Mn and V as two candidates and study in detail the possible N 2 reduction reaction (NRR) pathways for Mn-MoP and V-MoP. Our results revealed that Mn-MoP and V-MoP exhibit energy change values of 0.95 eV and 0.65 eV, respectively, with the first hydrogenation step being the potential-limiting step. Mn-MoP can efficiently suppress ∗H adsorption and reduce the competition of the hygrogen evolution reaction (HER) with the NRR; whereas, V-MoP cannot. Therefore, Mn-MoP is a better catalyst to realize the nitrogen reduction reaction. Overall, this work takes one step toward the NRR possibility of transition metal phosphides and provides some important insights and guidance to experiments.