Terahertz Time-Domain Spectroscopy(THz-TDS) combined with Simple Linear Regression (SLR) is utilized for the detection of potassium sorbate in milk powder. The THz spectra of potassium sorbate in milk powder are measured in time domain; and the absorption and index spectra are obtained in the frequency domain of 0.2-2.0 THz. The results show that potassium sorbate exhibits an obvious characteristic absorption peak at 0.98 THz. The SLR model is applied to identify the content of potassium sorbate in milk powder. The results indicate that the THz spectroscopy combined with SLR is efficient for detection of potassium sorbate content in milk powder.