A prompt gamma neutron activation analysis(PGNAA)set-up was developed for the elements detection in aqueous solution,which includes a 241Am-Be neutron source and a 4-inch BGO detector.The geometry of set-up is determined by a series of simulations with the MOCA code to improve the efficiency of the elements detection.The thermal neutron flux and the gamma-ray self-absorption are considered during the optimization calculations.Experiments were performed to validate the set-up using samples including chlorine and mercury,respectively.The result shows that the characteristic peak count has linear relationship with the chlorine and mercury concentration changing.The minimum detectable concentrations of chlorine and mercury were found as 54 mg/L and 51.4 mg/L,respectively. A prompt gamma neutron activation analysis (PGNAA) set-up was developed for the elements detection in aqueous solution, which includes 241Am-Be neutron source and a 4-inch BGO detector. The geometry of set-up is determined by a series of simulations with the MOCA code to improve the efficiency of the elements detection. The thermal neutron flux and the gamma-ray self-absorption are considered during the optimization calculations. Experiments were performed to validate the set-up using samples including chlorine and mercury, respectively The result shows that the characteristic peak count has linear relationship with the chlorine and mercury concentration changing. The minimum detectable concentrations of chlorine and mercury were found as 54 mg / L and 51.4 mg / L, respectively.