The invention discloses a set-top box as well as a method and a device for set-top box software upgrading. The method comprises the following steps of: S101, detecting whether an upgrading request is available or not in a code stream in real time when the set-top box receives a program, if so, executing the step S102; S102, judging whether a frequency point of a current program is in the frequency point of a downloading stream or not, if so, executing the step S105, and otherwise, executing the step S103; S103, hinting whether a subscriber jumps to the frequency point of the downloading stream for downloading or not, if so, executing the step S106, and otherwise, executing the step S104; and S104, then downloading upgrading data when the subscriber switches to the frequency point of the downloading stream, and writing the upgrading data into a memory of the set-top box after the downloading is completed. The method ensures that the subscriber can download the upgrading data while watching the program and have better experience, and has no influence on the subscriber to watch the program.