Organic amines (OAs) have gained substantial interest in atmospheric chemistry due to their distinctive acid-base neutralization characteristics for secondary organic aerosols and new particle formation. To address the need for sensitive and online analysis of OAs, including dimethylamine (DMA), diethylamine (DEA), trimethylamine (TMA), and triethylamine (TEA), in seawater, a home-built photoelectron-induced chemical ionization TOFMS, coupled with online derivatization and dynamic purge-release apparatus, has been developed. Sodium hypochlorite is used to derivatize high-solubility DMA and DEA, substituting hydrogen atoms with chlorine atoms to obtain more volatile derivatives, [DMA-H + Cl] and [DEA-H + Cl]. Sodium carbonate is used to reduce the solubility of the OAs in solution to enhance detection sensitivity. Microbubbles generated from 250 to 300 mL/min of zero air at the gas-liquid interface efficiently transfer dissolved OAs into the gas phase. Water vapor in the purged gas is ionized by photoelectrons to form (H2O)n·H+, which ionizes OAs and their derivatives to produce characteristic ions [OAs + H]+ or [OAs-H + Cl]·H+ characteristic ion. After optimizing the experimental conditions, the limits of quantification (S/N = 10) of the four OAs including DMA, DEA, TMA, and TEA can be as low as 1.1 0.68, 0.85, and 0.49 nmol/L, respectively within a 5 min analysis time, using only 5 mL of seawater sample. This method enhances sensitivity by over 5-fold and reduces analysis time to 21.7%, respectively, compared with conventional methods. Subsequently, this method was successfully applied to quantify 15 seawater samples from 5 typical marine environments, which demonstrates its practicability and reliability for analysis of trace amines in seawater.