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In transition metal oxides, the subtle modulation of charge carrier triggers the emergence of exotic electronic and magnetic properties. In the ferromagnetic metal SrRuO₃, experiment has shown a systematic and reversible control of both carrier density and crystalline symmetry through the ionic liquid gating induced protonation. The insertion of protons dopes the SrRuO₃, leading to a ferromagnetic to paramagnetic phase transition. In order to understand the protonation induced structural and magnetic phase transformations in SrRuO₃, we performed first-principles calculations. The proton intercalation leads to a significant splitting of the degenerated Ru t_2g bands, resulting in dramatically modified density of states. The lattice also shows a significant expansion with the intercalation of proton, consistent with the XRD results. The observed ferromagnetic to paramagnetic transition in SrRuO₃ can be understood within the Stoner model.