The invention provides an upgrading method and device of a control unit, wherein the method includes: receiving upgrade data of a version to be upgraded, storing the upgrade data that is received to abackup partition that is preset, reading the upgrade data from the backup partition when the upgrade data of the version to be upgraded is complete, and copying the upgrade data to an application partition to carry out version upgrading. According to the method, the upgrade data of the version to be upgraded is stored to the backup partition that is preset, the upgrade data is copied from the backup partition to the application partition to carry out version upgrading when the upgrade data is complete, an original application is never damaged if anomalies occur to the control unit upgrading process, it is avoided that writing the upgrade data directly to the application partition and overriding the original application directly with the upgrade data may lead to damage to the original application due to power-off, reading-writing flash failure and other conditions, control unit upgrading reliability is improved, and the upgrading method according to an embodiment of the invention is easy to implement.