A method for updating a reorder depth in robust header compression, comprising: when determining that a reorder occurs in data packets, a decompressor estimating a reorder situation, and determining whether a more robust reorder processing policy needs to be used according to the reorder situation; if the more robust reorder processing policy needs not to be used, maintaining a reorder depth value at the decompressor side; if the more robust reorder processing policy 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; after receiving the feedback packet, the compressor updating a reorder depth value at the compressor side according to the reorder depth value in the feedback packet, characterized in that before the decompressor determines whether a reorder occurs in data packets, the method further comprises: recovering the data packet according to a sequence number of the received data packet, verifying the recovered data packet, if the verification is successful, performing reorder determination; if the verification is failed, performing reorder restoring, and if the restoration is successful, performing the reorder determination; and if the restoration is failed, discarding the data packet and not performing the reorder determination; wherein the reorder restoring comprises: determining whether the reorder depth value at the decompressor side can be increased, if the reorder depth value at the decompressor side can not be increased, considering that the restoration is failed; if the reorder depth value at the decompressor side can further be increased, performing recovery calculation on the sequence number using a greater value as the reorder depth value at the decompressor side, recovering the data packet with a recovered new sequence number, verifying the recovered data packet, and if the verification is failed, considering that the restoration is failed, and if the verification is successful, considering that the restoration is successful and updating a restoration success number record. when determining that a reorder occurs in data packets, a decompressor estimating a reorder situation, and determining whether a more robust reorder processing policy needs to be used according to the reorder situation; if the more robust reorder processing policy needs not to be used, maintaining a reorder depth value at the decompressor side; if the more robust reorder processing policy 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; after receiving the feedback packet, the compressor updating a reorder depth value at the compressor side according to the reorder depth value in the feedback packet, characterized in that before the decompressor determines whether a reorder occurs in data packets, the method further comprises: recovering the data packet according to a sequence number of the received data packet, verifying the recovered data packet, if the verification is successful, performing reorder determination; if the verification is failed, performing reorder restoring, and if the restoration is successful, performing the reorder determination; and if the restoration is failed, discarding the data packet and not performing the reorder determination; wherein the reorder restoring comprises: determining whether the reorder depth value at the decompressor side can be increased, if the reorder depth value at the decompressor side can not be increased, considering that the restoration is failed; if the reorder depth value at the decompressor side can further be increased, performing recovery calculation on the sequence number using a greater value as the reorder depth value at the decompressor side, recovering the data packet with a recovered new sequence number, verifying the recovered data packet, and if the verification is failed, considering that the restoration is failed, and if the verification is successful, considering that the restoration is successful and updating a restoration success number record. recovering the data packet according to a sequence number of the received data packet, verifying the recovered data packet, if the verification is successful, performing reorder determination; if the verification is failed, performing reorder restoring, and if the restoration is successful, performing the reorder determination; and if the restoration is failed, discarding the data packet and not performing the reorder determination; wherein the reorder restoring comprises: determining whether the reorder depth value at the decompressor side can be increased, if the reorder depth value at the decompressor side can not be increased, considering that the restoration is failed; if the reorder depth value at the decompressor side can further be increased, performing recovery calculation on the sequence number using a greater value as the reorder depth value at the decompressor side, recovering the data packet with a recovered new sequence number, verifying the recovered data packet, and if the verification is failed, considering that the restoration is failed, and if the verification is successful, considering that the restoration is successful and updating a restoration success number record.