Abstract: In order to identify the stratigraphic structure characteristics of Sanjiang Plain in the north part of Zhoushan Island more accurately, efficiently and environmentally friendly, and support the urban underground space development in the north part of Zhoushan Island, the researchers in this paper adopted the high-density resistivity method to carry out the applied geological survey. The results showed that the stratigraphic structure of Sanjiang Plain was mainly composed of three layers, including Holocene Zhenhai Formation silt subclay layer, Upper Pleistocene Ningbo Formation sand gravel layer and Upper Jurassic subvolcanic rock crystalline fused tuff layer. The top boundary of the sand gravel layer and the crystalline fused tuff layer was "funnel-shaped" with shallow burial depth around the plain and deeper burial depth in the middle of the plain. F₁ hidden fault structure controled the southwest boundary of Sanjiang Plain, and F₂ hidden fault structure ran through the study area in a northeastward trend and damaged the integrity of the underlying bedrock layer. In this study, the stratigraphic structure characteristics, the buried depth of each lithologic layer and the distribution of buried fault structures in Sanjiang Plain in the north part of Zhoushan Island were basically ascertained. The formation structure divided by the high-density resistivity method was consistent with the existing drilling data, which verified the feasibility and effectiveness of the high-density resistivity method in the study of stratigraphic structure division. The study results could provide reliable geophysical basis for the development and utilization of the underground space in Sanjiang Plain in the north part of Zhoushan Island.