Water injection in offshore thin interbedded oil fields is a great challenge because of its high cost and difficulty in construction. Through long-term research and practice， separated layer self-source enclosed water injection technology is put forward to supplement energy. Based on the characteristics of offshore oil fields， the screening principles of target layer， water source layer and pilot water injection well group are formulated. We developed self-source enclosed injection pipe string and underground data monitoring system， such as measuring and adjusting， water quality monitoring， etc.， and has the huge advantages of multi-purpose in one well， low cost， green energy saving and quick effect. This technology can reduce costs related to drilling， platform facilities and surface water injection facilities， and effectively reduce water corrosion and reservoir damage. It has a wide range of reference and promotion significance in similar thin interbedded water injection oilfields offshore.