This paper deals with a possibility of a modeling of a block system. A created modeling tool contains a graphic editor of a track section configuration and a graphic editor of control algorithms, which serves on a writing of behavior algorithms of exterior devices of the block system. In order to the modeling of the block system was possible general models of basic exterior devices and a programming language for the writing of control algorithms to a source code form had to be created. It describes a work with different parts of the modeling tool and their possibilities on a selected example of an automatic block. The paper also describes an ability of to simulate a modeled block system activity and an ability to simulate the movement of th...