Based on the principle of single photon counting,the prototype for de tecting trace narcotics is designed and constructed according to the photo-induced delayed luminescenc e.The performance of the prototype is evaluated,and the results show that the dark count of the photomultiplier (PMT) is 11.5±0.7photons/s,and the system dark count is 11.7±0.7photons/s. The performance of the prototype on shielding stray light is excellent.The DL decay curves and parameters of the healthy personnel and the suspected methamphetamine per sonnel serum samples are measured by using the prototype,and the experimental results show that all the parameters between the two samples are obviously different.The prototype has t he advantages of high sensitivity and low sample consumption,except that the testing process is not i n direct contact with the sample,so it provides a powerful tool for detecting trace narcotics in biologic al samples.