For mass criticality control, accurate material accountancy and control must be kept in facility where significant amounts of fissile materials are processed. The computerized accountancy and control system was applied into the plutonium facility of PNC and has been improved according to the accumulation of fabrication experience. This system is being operated on real-time basis and also is very useful for the safeguards requirements. The source data for MUF analysis activities are obtained by processing the PIT data. The requirements, structures, and operational method of this system are described in this paper. (auth)