We studied Marsh Grassbirds (Locustella pryeri sinensis) and reedbed management from 2006 to 2009 in the Yalu River Estuary Wetlands National Nature Reserve, China. Common reed (Phragmites australis) management was monitored and habitat data for 11 variables from 53 nests were collected over a 4-year period. Calamagrostis epigejos was replaced by aquatic vegetation, none of the nests existed in 2008, and 10 of 11 habitat variables differed between before deep irrigation (>30 cm depth) (2006 and 2007) and after (2009) due to deep water. Mean ± SD clutch size was 4.5 ± 0.83, the daily survival rate was 92.3%, and overall nest success was 12.5%. Cover of total grasses accounted for 17.7% of the changes in nest height. Reed cutting and irrigation influenced the local breeding population of Marsh Grassbirds. Sound management practices could benefit Marsh Grassbirds and other grassland passerines.