The invention discloses a method and a system for updating patch software. The method and the system are used for communication devices where transmission plane software is separated from control plane software and management plane software. The method includes that a version management process triggers logging off of an oil version process to be updated and keeps data and data states of an upstream process and a downstream process of the old version process unchanged. The version management process triggers start of a new version process after the old version process to be updated is logged off successfully. The upstream process and the downstream process assist the new version process to restore the data and the data states. The system comprises a version management module and a data restoring module. By means of the method and the system, process grade control plane software upgrading can be conducted on the communication devices to avoid unnecessary service interruption caused by software upgrading. The method and the system improve business reliability and usability, avoid heavy economic loss caused by business interruption and improve user service experience.