The invention provides a detection method of drug taking. The detection method of drug taking comprises steps as follows: (A1) characteristic ion peaks of corresponding mass spectrometric detection ofdrugs are found according to influence of the drugs on human bodies; (A2) saliva of a suspected drug user is collected; (A3) an extracting agent is added to the saliva, and extraction and standing are performed; (A4) a liquid supernatant is sucked; (A5) the liquid supernatant is detected with a mass spectrometer, and the intensity of the characteristic ion peaks is acquired; (A6) whether the suspected drug user takes drugs is judged according to the intensity and a threshold value. The detection method has the advantages of being low in cost, free from complicated pretreatment, high in sensitivity and the like.