The present document provides a method and system for updating a reorder depth in robust header compression. The method comprises: when determining a reorder occurs in data packets, a decompressor estimating the reorder situation, and determining whether a more robust reorder processing policy needs to be used according to the reorder situation; if it needs not to be used, maintaining a reorder depth value at the decompressor side; if it needs to be used, updating the reorder depth value at the decompressor side to a greater value, and transmitting a feedback packet carrying the updated reorder depth value to a compressor; and after receiving the feedback packet, the compressor updating the reorder depth value at the compressor side according to the reorder depth value in the feedback packet.