Difference discrete variation principle and Noether theorem of discrete holonomic systems in event space were studied. By the difference discrete variation approach,the difference discrete variation principle of discrete holonomic systems in event space was derived. The discrete equations of motion of the system were established. The criterion of Noether symmetry of the system was given. The discrete Noether conserved quantity and the condition for its existence were obtained. Finally,an example was discussed to show the applications of the results.