The invention provides a measurement device and a measurement method for an in-situ time-resolved X-ray absorption spectrum. The measurement device mainly comprises an X-ray source, a first slit, a sound-light X-ray filter, a radio frequency emitter, a second slit, a front ionization chamber, a front ionization chamber signal amplifier, a sample to be detected, a rear ionization chamber, a rear ionization chamber signal amplifier, a data acquisition unit and a computer and the like. An X-ray source, the sound-light X-ray filter and the radio frequency emitter are used for generating a single-color X light beam; the front ionization chamber is used for measuring the strength before the X light beam penetrates through the sample; the rear ionization chamber is used for measuring the strength after the X light beam penetrates through the sample; the front ionization chamber signal amplifier, the rear ionization chamber signal amplifier, the data acquisition unit and the computer are used for acquiring data and processing the data. According to the measurement device and the measurement method, any mechanical part does not move in a measurement process, so that time-resolved measurement of the X-ray absorption spectrum can be realized; furthermore, the measurement precision on the X-ray absorption spectrum is relatively high.