The present invention relates to a method for distributing software, more particularly, to a method for distributing software based on software protection devices. Said software includes an upgrade program that is extracted from the software and placed into a user software protection device, and a protected program retained after the upgrade program is extracted from the software. Said protected program, upgrade program (which will be placed into the user software protection device), and the user software protection device are delivered to the user respectively. Then said protected program and upgrade program are installed and run jointly using leasehold information. Therefore, the software distribution process is protected and managed reliably, the developer's software distribution process is streamlined, the security of software protection is increased, the developer's development cost is reduced, and the usability of the software protection device is increased as well. Moreover, said protected program and upgrade program can be delivered through network so that the distribution cost can also be reduced.