ABSTRACT OBJECTIVE： To identify the main unknow impurity of Oxiracetam capsule and determine its content， so as to improve the standard of quality control. METHODS： Two-dimensional UPLC-IT-TOF-MS was adopted to qualitatively analyze the unknown impurity. One-dimensional liquid chromatogram analysis was performed on ST PAK C18 ES column with mobile phase consisted of 0.02 mol/L sodium dihydrogen phosphate solution at the flow rate of 0.5 mL/min. The column temperature was set at 30 ℃ ......