To make the optical systems simply controlled and easily realized in wireless optical communications, the design scheme of an automatic control device is put forward based on the optical closed－loop mode in which the volume and the inertia of the optical systems of collimating and beam expanding are small. Using the feedback control technology for reference, a light path of close－loop feedback is done with the pulse laser as control signal. The system is achieved by the micro controller unit (MCU) and the photoelectric detectors. Meanwhile, the hardware configuration and the software design scheme of the autocontrol device are presented, the former includes the MCU control system, stepping motor set, photoelectric detection system and feedback system, and the latter contains the control protocol and programmed function modules. Furthermore, the experimental results show that the automatic control device has the advantages of smooth operation and reliable automatic control. Thus, this study has practical value on the research of the light path collimating in wireless optical communications.