Abstract: The characteristics of offshore oil gas fields are bigger gathering radius, with long distance pipelines and lower deepwater temperature, which have brought new challengers to the running and management of offshore pipelines. This paper pays more attentions to the key problems of the mixing transportation technology of offshore pipelines, which includes gas condensate transportation technique, oil/water (heavy oil/water) flow.oil/gas/water multiphase flow, flow assurance technology (gas hydrate and wax deposit control), .severe slugging formation and control technology, pigging technology for gas condensate pipelines and multiphase increasing-pressure and measuring equipments and technology. More deeply presentation is given on these concerns. At last, this paper points out that applying advanced multiphase increasing pressure and measuring equipments and using high automatic system control, mixing transportation technique and flow assurance technique will provide technical support for the development of China's deepwater oil/gas fields.