This study presents the rational approaches to the process planning and scheduling for a building construction with computer systems. In the paper, the author put the focus on the methodology for planning and scheduling of activities in construction process, using a graphical presentation and system simulations with GPSS. The author has developed the graphical method of presenting the status of activities in construction process. This graph is called "Process Graph", which represents the activities, precedence relations among activities, resources, building elements, space and those interactions. Process Graph could be translated into GPSS language automatically, therefore it is very easy to develop a model of system simulation for construction processes. The methods described here were applied to planning of activities in reinforcing works.