We present a detailed study on the mechanisms of additive hydrogen for high repetition rate copper vapor lasers by solving the kinetics equations of self-consistency in space-time.The mechanisms of the increasing output power by adding small partial pressures of gaseous hydrogen to neon buffer gas are that: (1) the overall copper particles density is increased as the wall temperature increased; (2) the discharge current and the deposited power in the thyratron are decreased while maintaining the same stored input power,and making input power increased.On the other hand,when the additive hydrogen is superfluous (>(1—2)% neon) the plasma electron temperature and electron density decrease obviously owing to the vibrating excitation of hydrogen molecules impacted by the electron,and in this case the laser power decreases.