Abstract: Two submarine cables at the Yellow River underwater delta broke in November 2003, presumably owing to the relatively developed erosion ditches and landslide in the area. Geological survey was undertaken later in the Chengdao area in order to find out the reasons and conditions of the event. Various geophysical methods, such as multi-beam sounding, shallow profile exploration and side scan sonar survey, are applied. It is found that there do occur many erosional gullies on the sea bottom in the Chengdao area. Soft soil layers are common. Sediment disturbance are obvious in erosional trenches by the actions of wave and current. Based on the analysis of wave and current influences on seabed soil, the development degree of the erosional ditches and their relationship with water depth and soil properties are revealed. Upon the basis, triggering conditions of the seabed landslide are worked out. Increasing human activity is also the factor to be considered for the submarine landslide happened in the study area.