Abstract: Disclosed in the present application are a method and apparatus for detecting wafer defects which relates to the field of semiconductor. The method provided by the present application comprises: determining a repeating pattern unit and a non-repeating pattern unit in a Scanning Electron Microscope (SEM) image based on a SEM image to be detected and pattern units in a design layout; measuring the pattern units in the design layout, the repeating pattern unit, and the non-repeating pattern unit to determine difference information; and determining whether the repeating pattern unit and the non-repeating pattern unit have defects based on the difference information.