The invention relates to an optical delay line device and a terahertz time-domain spectroscopy system. The optical delay line device comprises a reflector set, a reflector base and a voice coil motor platform, wherein the reflector set is installed on the reflector base, and is used for scanning the delay of terahertz light, the reflector base is fixed to the voice coil motor platform, and the voice coil motor platform drives the reflector set to carry out linear reciprocating movement to carry out scanning. Due to the fact that the voice coil motor platform is used for driving the reflector set to scan the time delay of terahertz pulses, the defects that due to the fact that an electric horizontal-movement platform is limited by mechanical inertia, the electric horizontal-movement platform is low in transmission response speed, and the transmission response of the electric horizontal-movement platform is hysteretic are overcome, the different delay of the terahertz pulses can be scanned, the detection time of the terahertz pulses can be greatly shortened, a terahertz spectrum can be rapidly implemented, terahertz imaging can be rapidly achieved, the cost is low, operation is convenient, integration is easy, a time window is large, and the range of application of the terahertz time-domain spectroscopy system is greatly expanded.