Abstract: A measuring method and device based on the second harmonic for the whole area measurement of a wafer comprises three modes: a fixed-point measurement, a scanning measurement, and a combination of the fixed-point measurement and the scanning measurement. The scanning measurement solution measures the entire wafer under the premise of ensuring high measurement efficiency, obtain the position, size and relative density distribution of electrical defects, and achieve locating and checking of abnormal points on the wafer. A new formula system is provided for describing the second harmonic signal, so that the actual measurement results and the theoretical model are unified under the three modes of the fixed-point measurement, the scanning measurement, and the combination of fixed-point measurement and scanning measurement, so that the second harmonic metrology technology is no longer only a qualitative analysis method, but also a quantitative analysis method.