Objective To realize the simultaneous control of two laboratory instruments by a computer. Methods On the basis of analysing the mode of communication between computer and laboratory instrument, the author expanded the computer's COM interface through the USB / COM converter. Results The author realized a computer controlling MP280 CLIA chemiluminescence analyzer and anthos 2010 enzyme tester at the same time. Conclusion User can use computer's USB interface and USB / COM converter to achieve controlling multiple instruments and equipments at the same time, as long as the communication interface of equipment is open. This method has preferable potential application.