The invention discloses a hair pretreatment method belonging to the technical field of biological chemistry. The method comprises the following steps: cleaning hair by using a cleaning agent, and airing; crushing hairs into fragments, and finally, adding the hair fragments into digestive fluid, putting the digestive fluid into a water bath at the temperature of 60-100 DEG C for 5 minutes to 2 hours so as to hydrolyze the hairs, standing and cooling the digestive fluid to room temperature after the hydrolysis is finished, and detecting supernatant. According to the method disclosed by the invention, the hairs serve as a detection material, are easy to sample, non-traumatic and convenient to preserve and can be repeatedly sampled, the steps of a conventional hair pretreatment method are simplified and optimized, various components in the used digestive fluid do not influence with one another, the detection effect is good, the detection accuracy is high, the false positive condition is difficultly caused, and the misjudgment condition is avoided as much as possible in the detection process.