This paper designs and implements IPv6 protocol in WebitOS, an embedded real-time OS which is a self-owned intellectual property of Lab. of Embedded Technology, Northeastern University, China. WebitOS is developed on processor of ATmega128 MCU, and is designed to be a configurable embedded operating system and all of its function modules must be published in the form of software component. So the IPv6 module is designed to be in the form of software component too, and to be a co-existing module with IPv4 module. Then, the design of IPv6 header, IPv6 extend header, ICMPv6 header, IPv6 input process and output process, error message echo request and echo reply, neighbor solicitation and neighbor advertisement are fully implemented, respectively. Under the limited resource environment, IP address exhaustive problem is solved by the implementation of IPv6. Besides, the performance analyses between IPv6 and IPv4 are performed through some experiments.