Objective To establish a rapid determination method with LC-MS/MS for cocaine and its metabolite benzoylecgonine in hair. Methods Deuterated internal standards （cocaine-D3 and benzoylecgonine-D8） were added to the decontaminated hair. After the extraction by ultrasonication with methanol, the compounds were separated by the Restek Allure PFP propyl column, and cocaine and benzoylecgonine were simultaneously analysed in multiple reaction monitoring mode. Results The cocaine and benzoylecgonine in hair showed a good linearity in the range of mass fraction between 0.02 and 10.00 ng/mg with the limits of detection of 0.01 ng/mg. Conclusion The developed method is simple and rapid with a good selectivity, which is suitable for the determination of cocaine and its metabolite benzoylecgonine in hair.