The invention relates to a method for calculating a compression correction value in a time-triggered Ethernet. A unified state machine is used to control a calculation process, each newly arrived pcftime triggers the switching of the state of the state machine, and a result of a time correction value can be obtained immediately when an observation window ends. According to the method, specifyinga calculation method before compression calculation is not needed, the calculation method is dynamically adjusted with the change of the number of arrived pcf frames, therefore, buffering all the pcfframes before the calculation is not needed, and the compression calculation delay can be reduced. The calculation process is achieved by using the control of a simple finite state machine, the numberof required registers which store temporary data is small, and a hardware circuit is convenient to realize.