An understanding of the formation of organosulfates is required for elucidating the formation of secondary organic aerosols in atmosphere. Herein, we report a new feasible reaction pathway for the formation of organosulfates in the reaction of sulfuric acid (H₂SO₄) with acetaldehyde (CH₃CHO) catalyzed by dimethylamine ((CH₃)₂NH) using quantum chemical methods and reaction rate theory. We found that dimethylamine has a strong catalytic effect in the CH₃CHO + H₂SO₄ + (CH₃)₂NH reaction because the energy barriers of the CH₃CHO + H₂SO₄ + (CH₃)₂NH reaction are reduced by 18.28–23.08 kcal mol⁻¹ as compared to the CH₃CHO + H₂SO₄ reaction. The calculated results show that the CH₃CHO + H₂SO₄ + (CH₃)₂NH reaction can compete well with the traditional sink for CH₃CHO by hydroxyl radicals (OH), when the OH, H₂SO₄, and (CH₃)₂NH concentrations are 10⁴ molecules per cm³ during the night and 1.0 × 10⁶ and 3.2 × 10⁹ molecules per cm³ at below 240 K, respectively. The calculated results also show that the CH₃CHO + H₂SO₄ + (CH₃)₂NH reaction makes a limited contribution to the sink for sulfuric acid in the atmosphere. The present findings provide a new insight into the generation of organosulfates, which could be extended to other aldehydes with sulfuric acid catalyzed by amines in the atmosphere.