The invention relates to a digital TV set-top box, in particular to a method for realizing low power consumption and true standby function of a set-top box. The standby program in the method runs in a cache of a CPU of the set-top box and realizes the power consumption control on the set-top box during standby by the cache. The invention executes the running of the standby program by the cache ofthe CPU of the set-top box, reduces the frequency to the allowable lower frequency of a chip through adjusting the clock frequency of the CPU after entering a standby mode, and greatly lowers the consumption of energy by switching off relevant energy consumption components of a peripheral circuit during standby, thereby really realizing the environmental protection.