Abstract: The invention relates to the filed of the Internet of Things, and in particular, to an OTA differential upgrade method and system of a master-slave architecture. The method comprises: Step S1, obtaining an upgrade scheme, and determining a master-slave connection relationship and an upgrade manner according to the upgrade scheme; Step S2, downloading a differential upgrading file; Step S3, determining a processing mode of a master node according to the upgrading manner of a slave node; if the upgrading manner of the slave node is a first manner, the node flashes and restores the differential upgrading file and sends the differential upgrading file to the slave node, so that the slave node completes upgrading; if the upgrading manner of the slave node is a second manner, the master node flashes and restores the differential upgrading file and sends the differential upgrading file to the slave node for upgrading.