The invention provides a synchronous scanning streak camera temporal resolution measuring device and method, and aims at solving the problem that the confidence coefficient of a conventional testing method is low. The synchronous scanning streak camera temporal resolution measuring device comprises a femto second laser device, a first spectroscope, a fast recovery diode, a beam expanding lens, a second spectroscope, a first reflector, a second reflector and a length-measuring interferometer. The first spectroscope is arranged on the output light path of the femto second laser device, the fast recovery diode is arranged on the transmission light path of the first spectroscope, the beam expanding lens is arranged on the reflection light path of the first spectroscope, the second spectroscope is arranged on the output light path of the beam expanding lens, the first reflector is arranged on the transmission light path of the second spectroscope, the second reflector is arranged on the reflection light path of the second spectroscope, the length-measuring interferometer is arranged right behind the second reflector and used for measuring the moving distance of the second reflector in the light path direction of the second reflector, and the second reflector is a double-faced reflector. According to the invention, high-precision measurement of the resolution of a high-temporal resolution synchronous scanning streak camera is achieved.