Abstract: A method was developed for simultaneous determination of the residues of quizalofop-p-ethyl, chlorpyrifos, acetochlor amd imidacloprid in peanut by ultra high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample was purified with a combination of Nano-ZrO₂, C₁₈ and multi-walled carbon nanotubes (MWCNT), detected by UPLC-MS/MS, and quantified by external standard method. The results showed that in the range of 0.001-0.5 mg/L, the linear relationship between the mass concentrations of the 4 pesticides and their corresponding peak areas was good, with r≥0.9986. At the three spike levels of 0.01, 0.1 and 1 mg/kg, the average recoveries of the four pesticides in peanuts were between 82% and 109%. And the relative standard deviations (RSDs, n = 5) were between 2.8% and 9.0%. Among them, the limit of quantification (LOQ) was 0.01 mg/kg. This method was used to test 10 batches of peanut samples collected from large supermarkets and agricultural markets in Tai’an City. The results showed that the residues of the four pesticides in all samples did not exceed the maximum residue limits set by China. This method has the advantages of good purification effect, simple and efficient operation, high sensitivity, good stability and strong versatility. It is suitable for the simultaneous detection of four pesticide residues in peanuts.