Two-dimensional electrocatalytic materials for hydrogen evolution reaction (HER) have attracted considerable attention recently. However, most of the reported systems exhibit an inert basal plane, and extra engineering are needed to trigger the activity, greatly hindering their practical applications. Herein, using first-principles calculations, we identify a family of promising HER catalytic materials with high intrinsic activity in MXene Ti4X3O2 (X = C, N). We find that Ti4X3 are terminated by a mixture of OH* and 0* under standard condition by plotting Pourbaix diagram. The adsorption of atomic hydrogen on Ti4X3O2 exhibits a low Gibbs free energy difference, and the obtained activity barrier of Volmer-Heyrovsky step for Ti4N3O2 is only 30 meV, which indicates the excellent intrinsic HER activity. Furthermore, we explore the HER activity of Ti4X3O2 in aqueous solution through applying biaxial strain, and find that the low Gibbs free energy is well preserved, demonstrating the high stability of the intrinsic HER activity of Ti4X3O2 in solution environment. (C) 2020 Elsevier Inc. All rights reserved.