Abstract: PASC--1 is a reactor neutronics calculation programme system in whichAMPX--Ⅱ/SCALE--3 modules, ANISN, DOT3.5 and CITATION codes are linkedtogether for calculations on a CDC--CYBER computer. The IBM version sourcecodes of modules of AMPX--Ⅱ are translated into CDC version in FORTRAN--77and some changes are made for several modules. The PASC-1 system was first setup on CDC--CYBER--855 computer by the cooperation of CNDC and ECN resear-chers at Petten of The Netherlands in 1988, so called as "The Petten AMPX/SCALE Code System PASC--1". In 1989, the PASC--1 system was implemented and further extended on CDC-CYBER--825 computer at IAE. The new PASC--1 system can be used not only forthermal neutron reactors, but also for fast neutron reactors. It is briefly introducedin the paper.