Abstract: O⁶-Monoacetylmorphine, morphine, morphine-3-β-D-glucuronide in addicts’ blood samples were analyzed by solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The samples were extracted by extraction column (Oasis HLB), and then were flushed into the analytical column (Atlantis^TM dC18 (150 mm×3.9 mm×5 μm)) with methanol and water containing formic acid as mobile phase and morphine-3-β-D-glucuronide-d₃ as internal standard. The positive electric spray ionization, multiple reaction monitoring (MRM) mode were applied to analyze target compounds. Identification was based on the compound’s retention time and two pairs of precursor-to-product ion transitions. The results show that the limit of detections are 3-5 μg/L for morphine, O⁶-monoacetylmorphine and morphine-3-β-D-glucuronide. The linear relationship is well, and the linear correlation coefficient is greater than 0.997 5. The average recoveries are 80.6%-98.9% with the spiked levels of 50, 500, 1 000 μg/L, and the accuracies are -7.3%-9.1%. The method has high sensitivity and selectivity, which is suitable for analyzing the heroin and its metabolites in addicts’ blood samples.