Project schedule utilized at job-sites is, may be said, roughly divided into three phases: master schedule, detailed schedule and monthly schedule. This paper develops a master scheduling system supported by personal computer, which is based on time-space diagram, where production rate is represented as the gradient. This is because the ordinate plots the time while the abscissa plots the location (space) of each activity. The system uses precedence diagram and enables to represent the required distance among activities with regard to time and space as to make sure of the feasiblity as schedule. The system has been successfully applied to one of subway construction works.