An ultra-performance liquid chromatography coupled to quadrupole time of flight mass spectrometry（UPLC－QTOF MS） was established and employed for the untargeted screening of non-volatile organic compounds in washed recycled polyethylene terephthalate（rPET） flakes．Influences of pretreatment methods including choice of precipitation solvent，method of solvent removal，amount of test sample，and the chromatographic conditions including different mobile phases and eluent gradients on the determination of non-volatile organic compounds in rPET bottle flakes were investigated．A satisfied results could be obtained by using the following optimized condition or method：0.2 g rPET flakes was dissolved in 10 mL hexafluoro-isopropanol，20 mL methanol was used as precipitation solvent，the solvent was removed by nitrogen-assisted evaporation，methanol－0.1% formic acid water system was used as the mobile phase by gradient elution，and the data-dependent acquisition（DDA） mode was employed as data acquisition method．The qualitative analysis on the analyte was carried out by using MS database and secondary spectroscopy，while the semi-quantitative analysis was performed using compounds with similar structures．A total of 30 non-volatile organic compounds were detected in the rPET flakes，with amount of 0.038－4.92 mg/kg．The detected compounds included 27 types of non-intentionally added substances such as cyclic and linear oligomers，by-products of additives，degradation and contaminants，and the remaining 3 compounds might be associated with intentionally added additives．The recoveries ranged fron 66.0% to 80.4%，with relative standard deviations（RSD） not higher than 5.1%，indicating that this method has good stability and repeatability．24 types of rPET bottle flakes（rPET C and rPET N） from two different geographic manufacturers were detected by the established non-targeted screening methods with principal component analysis（PCA）．The（PCA） results showed that there were significant differences observed between rPET group C and group N，while 15 different types of compounds were detected．These results indicated that the recycled PET bottle flakes with the same type but having different sources may have different compositions．The UPLC－QTOF MS method was demonstrated to be accurate，reliable，simple and rapid，which could be effectively used for the analysis and safety assessment of non-volatile organic compounds in rPET intended for food contact applications.