According to the concept of autonomous decentralized system，this paper gives out a new train automatic control system，which is based on wirelesscommunication. In order to construct the communication based train control system．this paper proposes a high assurance method for system integration of current system and system proposed．In current automatic train control system(ATC)，the central ATC logic device produces position of each train and calculates permissible speed of each blocking section．Therefore the central logic device controls sDeed of all trains. On the other hand，in the communication basedsystem proposed by this paper，there is no logical central device and train can run completely autonomously．The trains itself detect the position and make thebrake pattern according to receive the position of the preceding train．In thechanging period of current ATC to the new system, we mtegrate these two heter-ogeneous systems. For getting the assurance high，the test is very important.Comparing with the conventional method，this paper proposes a high assurance method．