Abstract: This paper is concerning on the NEMA Standard Publication NU2-2001of Performance Measure-ments of Positron Emission Tomographs,which is the revised edition of the NEMA Standard Publication NU2-1994.Seven primary sections are included,such as:definitions,symbols and referenced publications;general;spatial resolution;scatter fraction,count losses and randoms measurement;sensitivity;accuracy:corrections for count losses and randoms;image quality,accuracy of attenuation and scatter corrections.