The multi point machines can change the high speed railway turnout. It describes the process of the design of the portable tester of multi point machine-traction system. The hardware platform of the tester is based on the LPC2214 chip of micro controller with ARM7 core and the software platform is established in the μC/OS-II real-time operating system. The tester master machine and the sensor slave machine makes up the tree topology and transmits through single core cable. The single core cable not only supplies power for sensors, but also transmits data between the master machine and the slave machine. According to the practical application, the tester could completely fulfill the design requirements. It is suitable for testing the multi point machines in the multi traction system.