Abstract: Objective To obtain the baseline data of local residents' cancer incidence and environmental terrestrial gamma-radiation dose around Sanmen Bay in Ningbo city from 2010 to 2014 before operation of Sanmen Nuclear Power Station. Methods The environmental radioactivity background values was monitored by adopting the Sodium iodide scintillator detection method and the relevant data on new tumor cases among local residents was collected from Zhejiang Chronic Diseases Surveillance Information Management System, and then a descriptive analysis was conducted on the overall incidence of new tumor cases, incidence sequence, incidence distribution by age, and radioactivity-sensitive tumors. Results The background value of the environmental terrestrial gamma-radiation dose in this area was 86.47±7.82 nGy/h and 6 270 new tumor cases were reported. The residents' tumor standardized incidence rate was 207.97/100 000 and the top five tumors were lung cancer (18.49%), liver and intrahepatic bile duct cancer (10.52%), gastric cancer (7.87%), colorectal and anal cancer (6.97%) and thyroid carcinoma (6.83%). The standardized incidence rate of Leukemia and thyroid carcinoma both belong to radioactivity-sensitive disease were 3.56/100 000 and 14.95/100 000 respectively. Conclusions The research showed the original environmental radioactivity background values and the incidence of radioactivity-sensitive tumors among the local residents in the area adjacent to the Nuclear Power Station around Sanmen Bay in Ningbo city within a radius of 30 kilometers objectively, also laid a firm foundation for long-term environmental radioactivity monitoring and evaluating the residents' health condition. Furthermore, we can reference the result to conduct the comparative study and association analysis later.