The Sanshandao Gold mine is a large operation near sea. Big water flow at the development stage caused mud burst and flooded roadways and shaft, threatening development and mining safety.In order to get an insight into the geological structure and hydro-geological aspects in the mine field, additional prospecting work was conducted.The hydro-geological conditions have been studied using different methods, concluding that the deposit is a typical fissure water-logged deposit. Water make-up sources include sea overflow, bittern and quaternary water. The results shown that no big instantaneous water flow would occur, posing no threat of sudden flooding of roadways and shafts. Dewatering method would be used for prevention and control of ground water in mine field.