Soil properties from mudflat at different exposure duration level were investigated during the drawdown period of Lake Dongting in January 2015. The ecosystem respiration was also measured using LI-8100 soil CO₂ flux system. After mudflat's exposing to the air, soil organic matters, soil nitrate nitrogen, soil ammonium nitrogen and soil total nitrogen contents increased at early time, then decreased. Dissolved organic carbon was the most important driving factor for the ecosystem respiration from mudflat during the drawdown period of Lake Dongting. The dissolved organic carbon value was monotonic increasing with the time of mudflat exposing to the air increasing, which strengthens ecosystem respiration from mudflat. The ecosystem respiration flux achieved peak value about 60 days after exposing to the air. The mean ecosystem respiration flux from mudflat was 0.72±0.55 μmol/(m²·s), exceeding the fluxes from poplars, reeds and farmlands. The exposed mudflat became the mainly active CO₂ releasing area in Lake Dongting during the drawdown period.