An emergency service over Voice over IP (VoIP) network is an essential condition, like the existing telecommunication services. To support for the emergency services, standardization works have been performed. The National Emergency Number Association (NENA) has been developing the framework and procedures for an emergency service for Non-IP based network, rather than protocols. In contrast, the Internet Engineering Task Force (IETF) has been only focused on end-to-end IP-based emergency calls. The NENA architecture is incompatible with the IETF protocols. To solve the problem, we design and implement a SIP-based VoIP emergency system by adopting the NENA architecture and by applying IETF protocols, for both IP-based Pubic Safety Answering Point (PSAP) and PSTN-based PSAP. It is implemented and tested under UNIX environment.