Polymer Monolithic Microextraction(PMME) based on poly(methacrylic acid-co-ethylene glycol dimethacrylate) is a very simple, efficient, and solvent less sample pretreatment technique developed by our group, and shows good biocompatibility when dealing with biosamples.In this work, direct coulping of PMME to electrospray ionization-quadrupole time-of-flight mass spectrometry (ESI-QTOF MS) was investigated and used for the preeoncentration and analysis of β-agonists in pork samples.Desorption solution and elimination of matrix effects by PMME would influence the ionization of the analytes and thus were studied carefully.In the positive-ion mode and in the multiple reaction monitoring (MRM) mode, the limits of detection (LOD) for β-agonists were found to be 0.08 ng/g (clenbuterol), 0.18 ng/g (salbutamol) and 0.26 ng/g (terbutaline) in pork, respectively, with good inter-and intra-day precisions.Parallel comparison was also carried out with the results obtained by PMME-HPLC-ESI-QTOF MS.PMME-ESI-QTOF MS was proved to be a rapid and accurate method for the determination of trace compounds in complex matrices.