The train control system is a safety-critical system. To assure its safety, it requires the testing process to cover all possible runs in its safety-critical scenarios. Existing methods of scenario modeling and test case generation cannot completely satisfy the requirement. The paper focuses on the methods of modeling safety-critical scenarios in train control system and the tools for automatically generating test cases for the system. UML activity diagram is extended with event-driven and time characteristic description mechanism to satisfy the requirement of modeling safety-critical scenarios. A simple path coverage criterion is also proposed to define the coverage of all possible runs in a scenario and a method is provided for automatic test case generation. The experiment on ground train control system shows the effectiveness and limitation of the proposed method.