An ultra performance liquid chromatography-tandem mass spectrometric（UPLC-MS/MS） method was developed for the rapid determination of 5 artificial sweeteners,6 iodinated X-ray contrast agents and caffeinein in various water samples（surface water,inflow and effluent for wastewater treatment plant）. The filtered water samples were extracted,and purified through HR-X solid phase extraction cartridges and separated on a Zorbax SB-C18 column. The determination of analytes was performed under multiple reaction monitoring（MRM） mode using acetonitrile-water（10 mmol/L ammonium acetate,0.01% formic acid） and acetonitrile-water（5 mmol/L ammonium acetate,1 mmol/L Tris） as mobile phases in positive ionization mode and negative ionization mode,respectively. The calibration curves of the target compounds were linear in the range of 5-5 000 μg/L with correlation coefficients more than 0.998. The recoveries of the target compounds in surface water,inflow and effluent were all between 70% and 120%,with relative standard deviations（RSD） of 0.8%-19.0%. The method detection limits（MDL） for three types of water samples were in the ranges of 0.43-13.8 ng/L,1.80 -34.8 ng/L and 2.30-134 ng/L,respectively. The method was successfully applied in the determination of artificial sweeteners,iodinated X-ray contrast agents and caffeine in different actual water samples collected from a wastewater treatment plant and its receiving river from Guangzhou city. Except for aspartame,iothalamic acid,iopromide and iomeprol,the other compounds were all detected with high concentrations. The established method is accurate,sensitive and simple,and is suitable for the determination of artificial sweeteners,iodinated X-ray contrast agents and caffeine in various environmental water samples.