In order to discuss the pathogenesis of deficiency and excess of heart qi in Neijing (Yellow Emperor’s Internal Cannon of Medicine), this paper points out that the deficiency and excess of heart qi in Neijing not only means the “excess of evil-qi and the deficiency of essence-qi”, but also can be explained by the local waxing and waning of essence and the accumulation of essence. Excess of heart qi refers to accumulation of heart qi, including excess of heart qi, accumulation of the Jingqi(essence qi)in the heart and superabundance of heart qi. Deficiency of heart qi refers to the insufficiency of essence or the weakening of function in the heart, including the deficiency of heart qi, decline of heart qi, slowness of heart qi, lack of heart qi and endopenia of heart qi.