The invention discloses a method for quantitatively detecting chromium in edible gelatin on the basis of terahertz time-domain spectroscopy. According to the method, firstly, multiple samples with different chromium content are prepared, then the multiple samples and a blank state are tested respectively by a terahertz time-domain spectral system, time-domain terahertz signals of the to-be-detected samples and the blank state in a preset frequency band are obtained, an absorption coefficient of each sample is calculated by performing Fourier transform on the time-domain terahertz signals, and a quantitative analysis model for the chromium content and the absorption coefficients is constructed with a least square method, so that the chromium content of an unknown sample can be calculated according to the absorption coefficient of the unknown sample. The samples are prepared conveniently and rapidly, addition of other substances is not needed in a detection process, a chemical processing process is not needed, the operation is simple, the analysis speed is high, and the cost is low; besides, by means of the constructed quantitative analysis model, a detection result is more real and more effective.