Abstract: Alkylamine carbonate nonionic-anion surfactant (C18A5C) in oilfield produced liquid was determined by HPLC with 3,6-dimethoxy-9-phenylcarbazole-1-sulfony chloride (DPCS-Cl) as pre-column derivatization reagent. After being filtered to remove the sediment, 10 L of the sample was concentrated to 5 mL and then extracted with N-butanol for two times. The extract was concentrated and set to 10.0 mL. 0.2 mL of DPCS-Cl acetonitrile solution (800 mg·L^-1) was added to the extract and the mixture derivatized at 60 ℃ for 30 min, the derivative was seperated on a Shim-Pack VP-ODS reverse chromatographic column, with a mixture of water and acetonitrile as the mobile phase. The extraction wavelength and exmission wavelenght of the fluorescence detector were 318, 440 nm respectively. The linearity range of C18A5C was 1.0-80.0 mg·L^-1, with detection limit of 0.05 mg·L^-1. Recovery rates obtained by standard addition method in the range of 91.6%-96.3%, and the intra-day and inter-day RSDs were 3.0%-4.9% and 4.3%-5.3%, respectively.