The present invention discloses an exchange method and an exchange system. The exchange system includes a service processor and an exchanger. The service processor is connected with the exchanger through a first back plate. The service processor is used for acquiring the data stream information of a service. The data stream information includes the destination address information of the service. According to the channel rate of the first back plate, the service is recombined to be at least one first sub-service with the rate thereof to be the channel rate. The exchanger is used for transmitting the first sub-service to the destination address. The optical exchange is conducted based on the channel rate of the back plate. Based on the exchange system, the data stream of the service is split into first sub-services with the rate thereof to be the channel rate, so that the scheduling granularity of the exchange system is improved. The electrical cross-connection capacity of the fine scheduling granularity in the exchange system is reduced. Furthermore, the power consumption of the exchange system is lowered.