Abstract: An efficient local firmware update (EL-FU) method is proposed to solve the problem of low efficiency in firmware updating of resource-scarce embedded system (RSES). A new local firmware is first written into memory by the debugger and written into the local update area reserved in external memory by the driver, and then debugged by the debugger. An update trigger module, a firmware update module, a directory adding module and a reminder module are added to the operating system, which only adds 3K bytes of code to the operating system. The local firmware is updated only by the debugger without using the burning tool and packaging the whole firmware. The reliability and stability of a resource-scarce Bluetooth audio on the chip system (MIPS32 M4K kernel and 128K bytes memory) whose firmware is updated with the EL-FU method, is tested. The efficiency of the proposed EL-FU method and the conventional JDO-FU (JTAG Debugger-based Overall Firmware Update) method to update firmware in the system is compared. At the same time, the efficiency of updating firmware of the same size in the RSES and a resource-rich embedded system (RRES) is compared. As the test results show, the RSES with the EL-FU method is reliable and stable; in the RSES, the firmware update efficiency of the EL-FU method is much higher than that of the JDO-FU method; the RSES can use the EL-FU method to overcome the limitation of less computing and memory resources and achieve the same firmware update efficiency as the RRES.