A data packet processing method and a related device are provided. The data packet processing method includes receiving, by a modem of a mobile terminal, an Internet Protocol IP data packet from a network; determining an online status of a data service of the mobile terminal; and processing, by the modem, the IP data packet according to a transfer protocol type of the IP data packet if it is determined that the data service of the mobile terminal is not in an online state, where the modem does not forward the IP data packet to an application processor of the mobile terminal if it is determined that the data service of the mobile terminal is not in the online state. Technical solutions provided in embodiments of the present disclosure help reduce standby power consumption of a mobile terminal, thereby improving product experience of users.