Update in maintenance, which is an important step in the software development cycle, is an necessary support of almost all the software in various application fields. Online update, which can reduce the cost and is convenient to the customer, is of great practical value. An idea of software update program, which can run across platforms, is brought forward and realized in this paper. The device of this program is mean to update across platforms, reduce the artifacial participation in update, and increase the ability of reuse of this program.