A vehicle-mounted device upgrade method, applied to a vehicle, wherein the vehicle comprises a first vehicle-mounted device and a second vehicle-mounted device, and the method comprises: processing, by a first vehicle-mounted device, a first data segment according to a first algorithm, to obtain a first check value, wherein the first data segment is any data segment in a plurality of data segments comprised in an upgrade file used to upgrade a second vehicle-mounted device, and the first check value is sent to the second vehicle-mounted device; wherein the first check value is a hash value, and: if the first data segment is the first data segment in the plurality of data segments in the upgrade file, the first check value is output data obtained by using the first data segment as an input of the first algorithm; and if the first data segment is a data segment other than the first data segment in the plurality of data segments in the upgrade file, the first check value is output data obtained by using the first data segment and a second check value as inputs of the first algorithm, wherein the second check value is obtained by processing a previous data segment of the first data segment according to the first algorithm; encrypting, by the first vehicle-mounted device, the first data segment by using a first key, to obtain a first encrypted segment; sending, by the first vehicle-mounted device, the first encrypted segment to the second vehicle-mounted device; receiving, by the second vehicle-mounted device, the first encrypted segment sent by the first vehicle-mounted device; decrypting, by the second vehicle-mounted device, the first encrypted segment by using the first key, to obtain the first data segment; when successfully verifying the first check value according to the first algorithm, storing, by the second vehicle-mounted device, the first data segment in the second vehicle-mounted device; and forming, by the second vehicular device, the upgrade file based on the first data segment for upgrade. processing, by a first vehicle-mounted device, a first data segment according to a first algorithm, to obtain a first check value, wherein the first data segment is any data segment in a plurality of data segments comprised in an upgrade file used to upgrade a second vehicle-mounted device, and the first check value is sent to the second vehicle-mounted device; wherein the first check value is a hash value, and: if the first data segment is the first data segment in the plurality of data segments in the upgrade file, the first check value is output data obtained by using the first data segment as an input of the first algorithm; and if the first data segment is a data segment other than the first data segment in the plurality of data segments in the upgrade file, the first check value is output data obtained by using the first data segment and a second check value as inputs of the first algorithm, wherein the second check value is obtained by processing a previous data segment of the first data segment according to the first algorithm; if the first data segment is the first data segment in the plurality of data segments in the upgrade file, the first check value is output data obtained by using the first data segment as an input of the first algorithm; and if the first data segment is a data segment other than the first data segment in the plurality of data segments in the upgrade file, the first check value is output data obtained by using the first data segment and a second check value as inputs of the first algorithm, wherein the second check value is obtained by processing a previous data segment of the first data segment according to the first algorithm; encrypting, by the first vehicle-mounted device, the first data segment by using a first key, to obtain a first encrypted segment; sending, by the first vehicle-mounted device, the first encrypted segment to the second vehicle-mounted device; receiving, by the second vehicle-mounted device, the first encrypted segment sent by the first vehicle-mounted device; decrypting, by the second vehicle-mounted device, the first encrypted segment by using the first key, to obtain the first data segment; when successfully verifying the first check value according to the first algorithm, storing, by the second vehicle-mounted device, the first data segment in the second vehicle-mounted device; and forming, by the second vehicular device, the upgrade file based on the first data segment for upgrade.