One of the most critical elements influencing lithography overlay accuracy is the distortion of the lithography projection objective. The distortion causes transverse magnification of the objective to change with the increase in the field of view, and the pattern exposed on the silicon wafer is displaced relative to its ideal position, which causes overlay errors. During the alignment and use of the objective, distortion must be detected and optimized. At present, the distortion of advanced lithography projection optics is less than 1 nm, and its high-precision measurement is a difficult point in this field. This paper examines the principles and characteristics of three widely used lithography distortion detection technologies-exposure measurement, aerial image measurement, and wavefront measurement-as well as their future development potential. To increase the accuracy and speed of distortion detection, multichannel detection technology is an important development path for lithography nodes of 16‒19 nm and below 16 nm.