Abstract: A new method for real-time detecting the rotation speed of high-speed rotating-mirror camera is proposed. This method acquires the time information of the rotating mirror by the laser’s capability of resisting the magnetic interference and being processed quickly. In order to gain a stable signal, an amplifier with limiting amplitude is needed to accommodate the wide range of the receiver power of the detector. An ASIC counter unit is adopted to meet the precision requirement and an embodied control module is used to realize the human-computer interaction conveniently. The experimental results show that the error can be restricted to nanosecond level and this system can improve one order of sensing precision than other sensing systems.