The response bandwidth is an important parameter to describe the frequency response characteristics of photoelectric detector. It characterizes the response capability of photoelectric detector for different modulated optical signals. The research is based on measurement of response bandwidth of photoelectric detector for acousto-optic modulation technology. Laser power is modulated, and photoelectric detector is used to detect modulated laser and record output voltage. Therefore, the response bandwidth of photoelectric detector can be determined through analysis. Such method is easy to operate and facilitates measuring the response bandwidth of photoelectric detector with low cutoff frequency.