A method of data processing, applied to a packet data convergence protocol, PDCP, layer, comprising: reordering a received PDCP data packet according to a serial number of the PDCP data packet; determining whether the serial number of the reordered PDCP data packet is inside or outside a Reordering_Window, in the case that the serial number of the reordered PDCP data packet is inside the Reordering_Window, delivering the reordered PDCP data packet to a robust header compression, RoHC, entity in a serial number order of the reordered PDCP data packet, and obtaining a data packet resulting from header decompression performed by the RoHC entity on the PDCP data packet, wherein in the case that the serial number of the reordered PDCP data packet is inside the Reordering_Window, the delivering the reordered PDCP data packet to the RoHC entity in the serial number order of the reordered PDCP data packet comprises: delivering the reordered PDCP data packet to the RoHC entity by using a first delivery mode, wherein the first delivery mode comprises: determining, in the serial number order of the reordered PDCP data packet, whether a PDCP data packet with the serial number of N is received in the Reordering_Window; in the case that it is determined that the PDCP data packet with the serial number of N is received in the Reordering_Window, delivering the PDCP data packet with the serial number of N to the RoHC entity; or in the case that it is determined that the PDCP data packet with the serial number of N is not received in the Reordering_Window, waiting until the PDCP data packet with the serial number of N is received in the Reordering_Window and delivering the PDCP data packet with the serial number of N to the RoHC entity; incrementing N in order of PDCP serial number cyclically, and repeating the determining, in the serial number order of the reordered PDCP data packet, whether the PDCP data packet with the serial number of N is received in the Reordering_Window; wherein N is an integer and is initially equal to 0. reordering a received PDCP data packet according to a serial number of the PDCP data packet; determining whether the serial number of the reordered PDCP data packet is inside or outside a Reordering_Window, in the case that the serial number of the reordered PDCP data packet is inside the Reordering_Window, delivering the reordered PDCP data packet to a robust header compression, RoHC, entity in a serial number order of the reordered PDCP data packet, and obtaining a data packet resulting from header decompression performed by the RoHC entity on the PDCP data packet, wherein in the case that the serial number of the reordered PDCP data packet is inside the Reordering_Window, the delivering the reordered PDCP data packet to the RoHC entity in the serial number order of the reordered PDCP data packet comprises: delivering the reordered PDCP data packet to the RoHC entity by using a first delivery mode, wherein the first delivery mode comprises: determining, in the serial number order of the reordered PDCP data packet, whether a PDCP data packet with the serial number of N is received in the Reordering_Window; in the case that it is determined that the PDCP data packet with the serial number of N is received in the Reordering_Window, delivering the PDCP data packet with the serial number of N to the RoHC entity; or in the case that it is determined that the PDCP data packet with the serial number of N is not received in the Reordering_Window, waiting until the PDCP data packet with the serial number of N is received in the Reordering_Window and delivering the PDCP data packet with the serial number of N to the RoHC entity; incrementing N in order of PDCP serial number cyclically, and repeating the determining, in the serial number order of the reordered PDCP data packet, whether the PDCP data packet with the serial number of N is received in the Reordering_Window; wherein N is an integer and is initially equal to 0. determining, in the serial number order of the reordered PDCP data packet, whether a PDCP data packet with the serial number of N is received in the Reordering_Window; in the case that it is determined that the PDCP data packet with the serial number of N is received in the Reordering_Window, delivering the PDCP data packet with the serial number of N to the RoHC entity; or in the case that it is determined that the PDCP data packet with the serial number of N is not received in the Reordering_Window, waiting until the PDCP data packet with the serial number of N is received in the Reordering_Window and delivering the PDCP data packet with the serial number of N to the RoHC entity; incrementing N in order of PDCP serial number cyclically, and repeating the determining, in the serial number order of the reordered PDCP data packet, whether the PDCP data packet with the serial number of N is received in the Reordering_Window; wherein N is an integer and is initially equal to 0.