Abstract: In the research of chemical pharmaceutical processes, there are still many seemingly ambiguous issues regarding redox reactions. Author proposed the concept of "hydrogen negative(H⁻)" by considering the sources, reduction mechanisms, and reducing abilities of sodium borohydride, and then extended it to other metal reducing agents such as LiAlH₄, Red-Al, DIBAL-H, Et₃SiH. The analysis indicated that their reducibility stems from the disparity in electronegativity between B, Al, Si, and H, which led to the generation of hydrogen negativity. Building upon the free radical theory of traditional catalytic hydrogenation, another polar reaction hypothesis was proposed, and the carbonyl reduction process in biocatalytic oxidation-reduction reactions was explained in detail, further confirming the rationality of the hydrogen negative theory. Meanwhile, based on the hydrogen negative reducing agent, it was inferred that the majority of oxidants were hydrogen oxygen positive(HO⁺) or reactive oxygen species(⁺O⁻), thereby revealing the shared characteristics of oxidants. Furthermore, an analysis was conducted on instances of enzymatic oxidation reactions which consistently demonstrates their association with reduction reactions. Guided by the theory of hydrogen negativity, various reactions involving oxidation-reduction had been reinterpreted, and more reasonable mechanistic hypotheses had been revised or proposed. The role of catalysts in oxidation-reduction reactions had been preliminarily explored. Finally, a precise definition of oxidation-reduction reactions was provided, dividing polarity reactions into substitution reactions and oxidation-reduction reactions, while elucidating that the fundamental characteristic of oxidation-reduction lies in the occurrence of "polarity reversal".