A method of determining request transmission priority subject to request content and transmitting request subject to such request transmission priority in application of Fieldbus communication framework in which the communication device determines whether the received requests have the priority subject to the respective content, and also determines whether there is any logical operation condition established, and then the communication device transmits the received external requests to the connected slave device as an ordinary request or priority request, preventing the slave device from receiving an important external request sent by the main control end or manager at a late time.