Because the absence of hardware support, almost all of embedded operating system are based on SDRAM in past time. With progress of embedded system hardware, embedded system can provide more substrative supports for embedded operating systems. In this paper we present an operating system microkernel for embedded system which can reside in the SRAM on chip. With progress of embedded system hardware, embedded system can provide more substrative supports for embedded operating systems. In this paper we present an operating system microkernel named SRAMOS for embedded system which can reside in the SRAM on chip. This microkernel can make the most of low power consumption of SRAM. The experiment results show that this microkernel performs better than the traditional embedded operating systems.