Abstract: The atom probe field ion microscope is a powerful tool in detecting the microstructures of materials. A software package for on-line control of the instrument and the atom probe data analysis has been developed in the Laboratory of Solid State Microstructures of Nanjing University. It comprises three different types of data accumulation programs, and the data can be analysed in the mode of mass spsctrum, composition profile and its autocorrelation analysis or ladder diagram, with which maximum information and flaxibility to view the data were achieved.