As one of the most widely used MXene, Ti3C2X2 (X= O, OH, F, Cl) is a promising 2D material for various catalytic reactions. Especially, Ti3C2O2Hx phase is known to be an excellent noble-metal free catalyst for hydrogen evolution reaction (HER). The conventional HER mechanism study of Ti3C2O2Hx was modeled with an isolated hydrogen reduction on the active sites of the catalyst surface. Recent density functional theory (DFT) studies reported the strong coverage-dependency of the hydrogen adsorption free energy and zero adsorption energy, which is the theoretically ideal condition for the highest HER activity1. Recent density functional theory (DFT) studies have reported the strong coverage dependence of hydrogen adsorption free energy and zero adsorption energy, for example, from the approximately linear relationship between the Hydrogen coverage ratio and the average adsorption energy, the ideal conditions for MXene(Ti3C2O2Hx) to achieve the highest HER activity can be theoretically obtained. Additionally, changes in the material interface generated in different conditions will affect the work function of the catalyst, and then affect the performance of the catalyst due to some deeper reasons, such as Fermi level and charge transfer efficiency2. Our study will focus on the two main points, hydrogen coverage and work function changes, and verify MXene(Ti3C2O2Hx) as an excellent catalyst for HER from a theoretical perspective.