The invention discloses a sample pretreatment method for detecting PPG in a PAM-containing oilfield extraction liquid. The sample pretreatment method comprises: taking a PAM-containing oilfield extraction liquid, detecting the total amount of PAM and PPG in the oilfield extraction liquid by using a liquid chromatography method; adding aluminum nitrate to the oilfield extraction liquid, shaking to completely dissolve the aluminum nitrate, and precipitating the white flocculent precipitate in the solution; adding H2O2, uniformly shaking, and placing for 2-5 min; and taking the supernatant so as to complete the sample pretreatment, and detecting the concentration/content of PPG in the supernatant by using a liquid chromatography method. According to the present invention, the sample pretreatment method can effectively eliminate the interference caused by PAM, has advantages of good repeatability, simple operation and low use cost, is particularly suitable for the sample pretreatment in the PPG detection of the PAM-containing oilfield extraction liquid, and can provide the technical support for the realization of the mechanism of the extraction rate increasing with the heterogeneous compound displacement and the guidance of the oil displacement system design and the scheme optimization.