Abstract: Geant4 is a Monte Carlo simulation program toolkits developed by CERN. It can be used in various fields such as high energy physics, medical physics, etc. For the applications of Geant4 in nuclear technology, some examples which simulate in accelerate physics, medical physics, HPGe measurement system and isotope dose distribution are discussed. The results show that Geant4 is competent in simulation for different field in nuclear technology.