Flood tide water surface profile （FTWSP） is the basis of water resources planning and water conservancy construction， and iscritical for the safety of local flood control as well. River terrain is an impact factor for the FTWSP and its change has a significant effect onFTWSP. Taking the river network in the West and North River Delta as the study area， the river terrain change in the past decades and itsimpacts on the FTWSP were explored using the one-dimensional hydrodynamic model . The results show that： （1） Under the influences ofhuman activities， especially the large-scale sand excavation since the late 1980s， the river terrain of the West and North River Delta hasbeen in a scouring stage， particularly in the 1990s； （2） Compared with that in 1999， the result of the FTWSP based on river terraindropped markedly in the top and abdomen areas in 2005 with a maximum decline of 1.8 meters， which reaches up to 18%， while it goesup but no more than 0.1 meter （2.5%） in the tail area； （3） The rising effect caused by the tide and water surface slope variation isstronger than the declining effect caused by river erosion is the major reason why the FTWSP of 2005 in the tail area is higher than that in1999. The results of this study can provide further reference for local water conservancy construction and flood control.