Spectrum detection and acquisition system and method for time-varying signal

The invention discloses a spectrum detection and acquisition system and method for a time-varying signal. The spectrum detection and acquisition system comprises a light source, a light modulator, a beam expander, a converging lens, a detector, a data acquisition system and a computer, wherein after being modulated by the light modulator, the light source is in the mode that the light intensity is subjected to sine/cosine changing along with time; modulated light irradiates a time-varying signal source after passing through the beam expander; reflected or transmitted light reaches the detector after passing through the converging lens; the data acquisition system acquires total light intensity information within a period of time through time integrals; and the computer saves corresponding modulation and detection information and performs corresponding operation to acquire the spectrum form of the time-varying signal. In combination with the light modulation technology and the Fourier transformation principle, time integral detection is performed on the time-varying signal, and the spectrum of the time-varying signal is acquired according to the intensity value acquired by the time integrals and the light modulation information. The spectrum detection and acquisition system is simple in structure, low in cost and high in detection signal to noise ratio, and can detect repeated time-varying signals.