Symbol　synchronization　is　a　key　technology　for　synchronous　demodulation　of　digital　modulation　signals.　Aiming　at　the　limitation　of　timing　error　detection　and　long　timing　time　in　the　closed-loop　Gardner　timing　recovery　algorithm,　the　timing　error　detection　method　is　modified,　and　an　improved　method　of　adding　gain　control　processing　is　proposed.　The　simulation　results　show　that　the　improved　algorithm　can　capture　timing　error　of　multi-level　modulation　signal,　significantly　reduce　timing　errors　and　shorten　timing　time.　The　steady-state　timing　jitter　is　an　order　of　magnitude　smaller　than　the　classic　loop.　The　timing　recovery　of　MQAM　signal　and　MPSK　signal　can　be　completed　well,　which　proves　the　good　applicability　of　the　improved　algorithm.　©　2020　The　Institution　of　Engineering　and　Technology.