Abstract: The invention relates to an inter-die high-speed expansion system and an expansion method thereof. The high speed expansion system comprises a cross-die expansion synchronizer and a direct-connection path connected with the expansion synchronizer, the cross-die expansion synchronizer is arranged on dies, the dies are connected through the cross-die expansion synchronizer and the direct-connection path, the cross-die expansion synchronizer is used for controlling data transmission, the data comprises a clock signal, a reset signal, a handshake signal and a data signal, and all the signals appear in pairs in a differential form. The system has good universality and low complexity, can realize the flexible expansion of interconnected dies, and can form a larger package level network, which lays a foundation for subsequent microsystem integration.