Taking the 200 000 DWT waterway dredging project of Fangcheng port for example, we analyze key factors influencing the dredging productivity in view of difficult degrees of rock excavation on severe cutter suction dredger‘Tianjing’, carry out a statistical analysis on the rock property indices including saturated uniaxial compressive strength, RQD, etc., and estimate the rock mass integrity index by the empirical formula. According to the rock properties of dredging engineering, we present the basic quality index of modified value reflecting the overall characteristics of dredged rock mass [BQ]TH. Based on the least square method, we establish the empirical formula on [BQ]TH and dredging productivity, forecast the dredging productivity, and obtain a good result using the empirical formula and back-propagation network.