The invention discloses a method for detecting a phthalic acid ester plasticizer in plastics. The method comprises the following steps: mass spectrometric detection is performed on the pre-treated plastics, wherein, the mass spectrometric detection condition comprises: an ionization mode: direct sampling-atmospheric pressure chemical ionization; a sampling mode: liquid sampling or direct solid sampling; when the sampling mode is the liquid sampling, the pretreatment is characterized in that the plastics are dissolved in an organic solvent, wherein, the organic solvent is one or more of tetrahydrofuran, cyclohexanone and dichloroethane; when the sampling mode is the direct solid sampling, the particle size of the plastics is less than 1mm. The method can simultaneously detect four phthalic acid ester plasticizers in a quantitative mode, in the detection method, a sample pretreatment method is simple, detection time is short within 0.2 minutes, speed is fast, sensitivity is high, and resolution rate is high.