The invention discloses a pretreatment method for determining benzene series in a dairy product. The method comprises the following step: after v1 milliliters of acetonitrile is added into a container loaded with m grams of a sample to be measured, the container is enclosed, and volume of the enclosed container is v milliliters, wherein m/v1 is 8-12, and v/m is 3-5. The invention also provides a method for detecting benzene series in a dairy product after pretreating the dairy product to be measured by the above method. The method for detecting benzene series in the dairy product after pretreating the dairy product to be measured by the pretreatment method has high accuracy, sensitivity and precision and low detection limit.