The hydro-junction for water diversion project located at branch entrance of the lower tidal reach usually faces flow condition problem through sluice gate.Due to limited land conditions,the hydro-junction has to be built closed to the main river outside the branch entrance and keeps an open layout.As a result,branch mouth flow is significantly affected by the asymmetric tidal flow of main river and the cross flow at the entrance area of the sluice gate.Based on Jiepai junction,downstream and upstream flow condition is studied.