Abstract: This invention provides a load-balancing structure for packet switches and its constructing method. In this method, the structure based on self-routing concentrators is divided into two stages, that is, a first stage and a second stage fabric. A virtual output group queue (VOGQ) is appended to each input group port of the first stage fabric, and a reordering buffer (RB) is configured behind each output group port of the second stage fabric. Packets stored in the VOGQ are combined into data blocks with preset length, which is divided into data slices of fixed size, finally each data slice is added an address tag and is delivered to the first stage fabric for self-routing. Once reaching the RB, data slices are recombined into data blocks. This invention solves the packet out-of-sequence problem in the load-balancing Birkhoff-von Neumann switching structure and improves the end-to-end throughput.