The invention provides a method for online upgrading of cloud storage system firmware. The specific operation process includes the steps that a cloud storage system sends a firmware upgrading request for a bottom layer device, a system administrator submits the request to an upgrading control module, the upgrading control module informs an upgrading application module of a device with the firmware to be upgraded after receiving the request, and the upgrading application module analyzes the current service application condition and enters the upgrading service starting mode. Compared with the prior art, the method for online upgrading of the cloud storage system firmware can meet all the service continuity requests, and services can not be stopped; all local and allopatric storage devices in the cloud storage system can be conveniently upgraded, the method is an automated process which is easy to maintain and manage, the application range of the method is wide, the method can be suitable for upgrading of other computer operation systems, and practicability is high.