Shunt　Active　Power　Filter　(SAPF)　with　LCL　output　filter　is　a　typical　current　tracking　control　system.　This　article　explores　a　new　control　method　for　fast　tracking　of　compensation　current　and　suppressing　its　resonance.　The　state-space　model　is　first　established　in　the　synchronous　rotating　d-q　coordinate,　which　can　make　the　active　and　reactive　power　components　decoupled,　and　at　the　same　time　the　harmonic　current　can　be　directly　extracted,　thus　the　harmonic　detection　and　compensation　control　in　the　SAPF　system　are　unified　in　the　same　realization.　With　the　observer-based　feedback,　the　dynamic　response　and　stability　of　the　system　can　be　improved　through　pole　placement　in　state　feedback,　while　effectively　suppressing　resonance　and　reducing　the　damping　loss.　Simulation　results　are　given　to　verify　the　effectiveness　of　the　system.