Abstract Two-dimensional (2D) transition metal carbonitrides (MXene) have attracted growing interest in electrocatalytic hydrogen production due to its structural and electronic properties. In this work, the hydrogen evolution reaction (HER) activity of all 64 O-terminated ordered double transition metal carbonitrides in the form of M′2M″CNO2 (M′ = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta; M″ = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta) has been investigated by well-defined density functional theory (DFT) calculations. The results indicate that there are 11 M′2M″CNO2-MXene candidates whose HER performance is superior to that of Pt. Moreover, according to the stability screening, it is proved that Ti2NbCNO2, Mo2TiCNO2, and Ti2VCNO2 are more stable than other candidates. Especially, Ti2NbCNO2 have the potential to be perfect HER catalyst with the small Gibbs free energies of hydrogen adsorption (ΔG H) value of 0.02 eV, abundant catalytic sites on the C-side, and better stability. This work paves the way on designing excellent HER catalyst candidates based on M′2M″CNO2-MXenes.