More than 4 billion tons reserves has been found in China´s Bohai Bay. However, most of the reserves are from heavy oil, which is hard to develop. The offshore heavy oil development could neither directly use onshore experience for the reference nor learn from international example. In this paper, the main challenges were analyzed and presented for offshore heavy oil development based on the characteristics of offshore oil field. The advanced heavy oil exploitation technology was integrated into the technology system, which was successfully introduced to develop the offshore heavy oil field named by international experts as one of the most challenging technologies in the 21st century. With the novel "THREE ONE MODE" and "BEE MODE" developed, many marginal oil fields can be developed economically in Bohai Bay. And the Optimized Fast Drilling Technology adapting to offshore oilfield development was developed which could significantly reduce the drilling cost. In order to achieve the further growth of producing rate and enhanced oil recovery in Bohai oil field, the novel mode of offshore heavy oil efficient development was established after a long-term technology research and field practice. Different to the conventional development mode, this mode does not emphasize the primary, secondary, and tertiary recovery stages. It is a series of technologies which integrate, optimize, innovate and comprehensively apply in the three stages to increase production rate in early stage and prolong the high speed development time. It makes early stage water flooding, polymer flooding, polymer injection while water flooding as the policy of development technologies. Polymer flooding,as the main EOR technology, with drilling and production support technology system in multilateral wells, limited sand management and electric submersible progressive cavity pump technologies are integrated in the oil field operation to obtained the maximum benefits in the minimum time. With the efficient development mode of offshore oil field, NB35-2 heavy oil field in Bohai Bay, with the most viscous heavy oil in the world, was successfully developed. And currently the mode has been widely applied to more offshore oil fields. The theory and practice offers not only a novel method to develop China offshore oil field but also new ideals for the development of global offshore oil fields, especially for the heavy oil fields.