Abstract: The new computer software system INDO2000 used for personal assessment of occupational exposure due to intakes of radionuclides is described in this paper. This software system refers to metabolic models and parameters from the ICRP series Publications 56,66,67,68,69,71,78 and etc. This system adopts matrix algorithm that is adapted to run on microcomputer. VC++ is taken for compiling this software, which can run under Win95 or higher microsoft's operating system. This system can convert the measured values into intake, effective dose and other quantities used in assessment. It is applicable for routine individual internal dose assessment for radiation workers. This system uses new models and parameters. It can be used to solve recycling and non-recycling compartment models directly and can be used to estimate and assess individual internal dose accord with ICRP ’s recommendation in 1990 and international basic safety standards for protection against ionizing radiation and for the safety of radiation sources in 1997. Furthermore, this software runs under windows’ operating system, and graphic interface makes it friendly and more convenient.