The flow,sediment and topographic conditions of Jingjiang reach in the lower Yangtze River are complex.Establishing a flume model,we carry out an experimental research on the edge scouring of bed protection mattress in Jingjiang reach,including the effects of velocity,ballast condition and bed protection mattress width on the maximum depth and the underwater slope stability coefficient.We also put forward a new scouring depth calculation formula.The underwater slope stability coefficient is determined to be 0.5 in Jingjiang reach.The research provides an important basis for the determination of the length of the bed protection mattress.