Grating interferometers are becoming important positioning instruments in advanced node lithography machines owing to their high precision and robustness. To meet ultrahighly accurate positioning demands in the worktable of ≤14-nm node lithography machines, homodyne and heterodyne grating interferometry technologies and core systems with multidegree-of-freedom (multi-DOF) and nano/subnanometer metric accuracy were reviewed. Furthermore, a six-DOF positioning system in a current lithography machine enabled by an optimal configuration of “four gratings-four reading heads” was illustrated. Finally, errors in grating interferometers, including environmental error, installation error, and instrument inherent error were briefly discussed, and key challenges in error modeling, separation, and compensation were reviewed for achieving subnanometric accuracy and long-term accuracy stability. Hopefully, this study can provide preliminary guidelines for improving the accuracy and constructing various systems of grating interferometers.