Abstract: Packet-level multi-path transfers can cause packets reordering at the destination, this profoundly affects TCP performance. Addressing with this problem, reordering performance under multi-path transfers with Round-Robin packet assignment is analyzed in the view of queuing theory. The influence of path difference and path numbers on reordering performance under multi-path transfers is discussed with respect to three criterions: disorder rate, resequencing time and end-to-end total time. Results demonstrate that it is preferable to make paths with closer transmission rate for two paths transfers, and the paths number dose not exceed four to significantly improve the reorder performance if the paths have the same transmission rate.