Photoelectric detection system is the core component of a detector,and is widely used in photo-metric measurement and spectroscopy monitoring.Response time of a photoelectric detection system reflects the fastest response limit of the system in detection.Thus,an accurate measurement of the response time is very important for application.This work shows a method for accurate response time measurement of a photoelectric detection system.Here,a tunable diode laser with a wavelength of 763 nm,usually used in spectroscopy,is used as the light source and is tuned with a square wave.The response time is measured.The results indicates that the resistance of the oscilloscope can influence the response time of the system.The response time of the photoelectric detection system is measured as 4.5 μs when the resistance value is 50 Ω.The response time can be shortened if the resistance value reduces.This work provides a response time measurement method of a photoelectric detection system,which is a basis for the choice of detection system in application.