Disclosed is a transient-state THz spectrometer applied to cells and biological macromolecules, including a femtosecond laser amplifier. A femtosecond laser output by the femtosecond laser amplifier is divided into two beams of pump light and probe light after passing through a beam splitter of which a transmission-reflection ratio is 7:3, the pump light is focused to irradiate a gap between electrodes of a nonlinear photoconductive antenna and emit a terahertz wave after successively passing through a half wave plate, a silver-plated reflector and a first lens, the terahertz wave forms a terahertz wave collineation after successively passing through a second lens, a slab waveguide, a third lens and an ITO film, the terahertz wave collineation and the probe light form a probe light collineation of wavefront tilt which is perpendicularly incident on a ZnTe crystal and detected and recorded by using a CCD camera.