The emergence of novel drugs and the continuous expansion of the scope of the types of drugs under control have greatly increased requests for screening of a range of drugs in hair. Here, a multi-analyte method for the detection and quantification of 88 psychotropic drugs in the hair of addicts in drug abstinence was developed and fully validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Hair samples (25 mg) were washed, cut into pieces, cryogenically ground, and extracted in methanol. The extracted analytes were separated on an Allure PFPP column (100×2.1 mm, 5 mm i.d., Restek, USA) and analyzed by LC-MS/MS in multiple reaction monitoring mode. The limits of detection and limits of quantification ranged from 0.1 to 20 pg/mg and 0.2 to 50 pg/mg, respectively. The intra- and inter-assay precisions (RSD) of all analysis ranged from 0.9 to 14.9% and 1.9 to 15.9%, respectively. Accuracy values were 100±20%. The extraction recovery of quality control samples ranged from 50.9% to 99.6% for all analytes. The matrix effects for all analytes ranged from 46.8% to 99.7%. The method was successfully used to analyze 1,865 hair samples from addicts in drug rehabilitation at their own communities.. Among the samples, 129 cases were positive; the majority of positive cases were from males (78.29%), 92.25% of whom were over 35 years old. Traditional drugs, like methamphetamine and opioids, accounted for most positive cases, and 27 of the abstinence cases with a use history of methamphetamine were still positive. In addition to abused drugs, like methamphetamine, morphine, and cocaine, the sedative hypnotic and psychotherapeutic drugs, including clonazepam, alprazolam, estazolam, zolpidem, and quetiapine, were detected in 26% of the hair samples, suggesting that these addicts may have insomnia and mental problems such as depression and psychosis, probably due to the long-term effects of drugs and withdrawal reactions. Three synthetic cannabinoids were also detected in 4 (2.7%) cases. A total of 37 cases were positive for methadone, tramadol, and dextromethorphan, reflecting a new trend of alternative drug use when traditional drugs were not easy to obtain during the COVID-19 outbreak.