The coastal long-distance tide level in dredging projects can not be controlled in real time,which limits precision of dredging depth.To resolve this difficult problem,by analyzing such key parameters as the datum transfer,tidal harmonic constants,the number of residual water level selection and correlation,with the dredging project of Dafeng port channel in Yancheng this paper puts forward a method of calculating coastal long-distance tide level based on corrected residual water level and verifies it in dredging projects.