On October 17th, the 6th national nuclear technology and application was held in Suzhou ,Jiangsu province. Fu Kai, from the nano fabrication platform,Suzhou Institute of Nano-tech and Nano-bionics (SINANO), CAS, won the distinguished paper prize. In his paper, Time response of GaN Schottky detector with a large area to X ray has been studied. Using a Fe-doped GaN high resistive film to make the detecor, the time response under different bias has been tested. For the measured results, a theoretical model of time response of GaN Schottky detector to X-ray irradiation has been proposed, and its internal mechanism has been studied with a very good fitting results.