In existing equipment vehicle transmission test bed can be controlled only by 8031 SCM and data can not be transmitted from SCM to PC. In order to take most advantage of available equipment, data transfer between PC and Multi SCM is put forward. By this way, torque of eddycurrent dynamometer can be controlled by PC programs and satisfy the needs of torque convert experiment. Making use of Dynamic Link Library 8250 registers can be read and written directly. Programs can set the ninth bit easily without Microsoft Communication Control. Data are transmitted between PC and Multi SCM though RS232 COM successfully by using Visual Basic programs. Cost and time are sharply reduced.