Mangrove wetland ecosystem in Quanzhou Bay in Fujian Province  is newly restored with a regular semidiurnal tide. Soil CO₂ concentration in the mangrove soil was determined by Li-840 portable gas analyzer, and periodic characteristics of soil CO₂ emission was investigated. The soil CO₂ flux in the wetland soil was relatively small because the mangrove was young. The change trends of soil CO₂ concentration and flux with time were consistent in Kandelia obovate and Aegiceras corniculatum communities in the intertidal periods. The CO₂ concentration and flux in the wetland soil were 557.08-2211.50 μmol·mol^-1 and -0.21-0.40 μmol·m^-2·s^-1, respectively. The average CO₂ flux in the wetland soil was 0.26 μmol·mol^-1·s^-1 in the intertidal of morning and evening tides (early intertidal) and -0.01 μmol·m^-2·s^-1 in the intertidal of evening and morning tides (late intertidal), respectively. At the same time after the tide, the concentration and flux of CO₂ in the mangrove soil in early intertidal was higher than that in late intertidal. In early intertidal, the relationship between the flux and instantaneous concentration of CO₂ in the wetland soil was expressed as a bellshaped curve, and CO_2 flux increased first and then decreased with the increasing CO₂ concentration, which was in conformity with Gaussian distribution.