The invention discloses a high-definition digital STB which comprises a central controller, a main STB chip, a network card, a USB interface and a cable modulation and demodulation assembly, wherein the main STB chip is in communication connection with a storage module and a memory, the central controller controls the main STB chip, the cable modulation and demodulation assembly and the network card, the storage module is provided with the USB interface, and the network card and a WIFI radio frequency circuit transmit signals. The high-definition digital STB has the advantages that the structure is simple and compact, the cable modulation and demodulation assembly is used to reduce the size of the STB, the production cost is reduced, the STB can provide convenient network and television services for users, the expansibility is high, functions including network TV, webpage browsing, media play and interaction play on demand are supported, and signal transmission and reception are rapid.