The present application relates to a terahertz time-domain spectroscopy system. In this terahertz time-domain spectroscopy system, the femtosecond laser light radiated by the femtosecond laser is collimated by a first diaphragm, and then is split by a beam splitter into a pump light and a probe light. The pump light passes through the first light path module to generate a terahertz pulse, and the probe light passes through the first light path module to generate a linear polarization probe light having the same optical distance as that of the pump light. The linear polarization probe light and the terahertz pulse are combined by a beam combiner to obtain a light beam to be detected carrying the terahertz pulse information. Two electro-optical crystals with the same thickness are used in a detection device simultaneously. Changing the crystal axis angle of the two electro-optical crystals, there is a phase compensation to the two components o light and e light of the probe light, so as to realize linear detection to high power terahertz pulse and improve measurement accuracy.