Microcystins　(MCs)　are　cyclic　heptapeptide　toxins　and　tumor　promoters　produced　by　cyanobacteria,　which　threaten　the　health　of　humans.　In　this　study,　magnetic　porous　β-cyclodextrin　polymer　(Fe3O4@SiO2@P-CDP)　was　synthesized　and　characterized　by　transmission　electron　microscopy,　scanning　electron　microscopy,　energy　dispersive　X-ray　spectrometry,　Fourier　transform　infrared　spectrometry,　X-ray　diffraction,　nitrogen　adsorption　porosimetry　and　vibrating　sample　magnetometer.　The　synthesized　Fe3O4@SiO2@P-CDP　particles　were　then　used　for　magnetic　solid-phase　extraction　(MSPE)　of　MCs　from　environmental　water　samples,　and　exhibited　excellent　extraction　performance,　especially　for　MC-RR.　Coupled　with　high-performance　liquid　chromatography　with　tandem　mass　spectrometry　(HPLC–MS/MS),　a　simple,　efficient　and　sensitive　method　for　determination　of　trace　levels　of　MCs　was　established.　After　the　optimization　of　conditions,　wide　linear　ranges　(2.0–1000 pg mL−1),　good　linearity　(r2 ≥ 0.9996)　and　acceptable　repeatability　(RSD ≤ 9.4%,　n = 5)　were　obtained.　The　limits　of　detection　(LODs,　S/N = 3)　and　limits　of　quantification　(LOQs,　S/N = 10)　for　three　MCs　(MC-LR,　MC-RR　and　MC-YR)　were　in　the　range　of　1.0–2.0 pg mL−1　and　2.0–5.0 pg mL−1,　respectively.　Typical　water　samples　were　analyzed　by　the　developed　method,　and　trace　levels　of　MC-LR　and　MC-RR　were　detected.　The　results　demonstrate　that　the　developed　method　has　great　potential　for　the　determination　of　MCs　in　complicated　matrix.　©　2017　Elsevier　B.V.