Xylem sapflow of Avicinia marina (Forsk.) Vierh (A. marina) and environment factors were investigated over a year period (June 2011 to May 2012) by continuous sapflow density (SFD) measurements in Zhangjiang estuary in Yunxiao County of Fujian province, China. Diurnal SFD patterns for A. marina belonged to single curves following the variation of photosynthetically active radiation (PAR) and vapor pressure deficit (VPD,) but time lag between sapflow and PAR as well as VPD in both a wet month (summer) and a dry month (winter) are discussed .PAR exhibited diurnal peak values earlier than sap flow by 30 min (winter) to 60 (summer). However, VPD lagged behind sapflow by 30 in winter and earlier than sap flow by 30 min in summer. The sapflow rate of A. marina was much higher than those of terrestrial tree species. However, the daily water use was still conservative. Daytime half-hourly mean stand sapflow was positively linearly correlated with photosynthetically active radiation (PAR) and vapor pressure deficit (VPD) in during the study period (all P<0.001), whereas daily daytime mean stand transpiration was less tightly coupled to PAR and VPD, especially in the winter. A pronounced hysteresis was observed between stand sapflow and PAR or VPD, but the extent of the hysteresis varied seasonally and between species. However, the mechanisms and ecological implications of mangrove water use deserve further investigation.