The development of cost-effective hydrogen evolution reaction (HER) electrocatalysts has become pivotal in hydrogen production field. Because of the remarkable catalytic performance of Pt metal, developing low proportion Pt-based electrocatalysts should be very meaningful for entrepreneurs and scientists. In order to further decrease the economic cost, the HER electrocatalytic performance of low metal ratio Pt-doped MC2(M=Mo, W, and Cr) structures is investigated by first-principles calculations. It merits our attention that in monolayer WC2 when a Pt atom replaces a W atom, where HER occurs, the structure has a lowest overpotential of only 0.03 V, which is much lower than the reported value of pure Pt (111) (0.09 V) and the lowest value (-0.31 V) of WCx(x=1–4). It can be observed that some energy bands of Pt-WC2 cross the Fermi level, resulting in remarkable electronic conductivity. Specifically, Pt-WC2 shows good mechanical, dynamic, and thermal stabilities. Thus, single Pt modified monolayer WC2 can serve as an efficient economic electrocatalyst for HER. These findings can support strong theoretical basis for the experimental researches to develop a kind of excellent quality and reasonable price catalyst in the future.