The invention discloses a business exchanging and mapping system for a packet optical transmission network, sequentially comprises a business input module, an input end exchanging module, a mapping transmission module, an output end exchanging module and a business output module in the direction of a signal flow, and a scheme of numbering transmitted businesses according to different business types, granularity sizes, priorities and reliability requirements, and selecting a corresponding output port according to the number when in exchange, and relates to an assembling, segmenting and recovering method for mapping the different types of businesses on a same transmission line in a unified manner. Hereby, unified mapping and exchanging of the businesses with multiple business types and granularity sizes are completed. In addition, the situation that transmission is performed in an optical layer when the business granularity is large and transmission is performed in an electric layer when the business granularity is small is achieved, utilization ratios of resources of the optical layer and the electric layer are improved, the load pressure of electric layer equipment is reduced, and network cost is lowered.