In recent years, Session Initiation Protocol (SIP) is more and more popular. However, there are many security problems in the Session Initiation Protocol. In 2005, Yang et al. [9] proposed a secure authentication scheme for Session Initiation Protocol. This authentication scheme is based on Diffe-Hellman [2] concept, so the computation cost of this authentication scheme is very high. In order to improve this shortcoming, Durlanik et al. [3] also proposed an authentication Scheme using ECDH in 2005. However, the computation cost of this authentication scheme is still very high. In this paper, we propose an efficient nonce-based authentication scheme. The computation cost of this authentication scheme is lower than Yang et al. s authentication scheme and Durlanik et al.s authentication scheme, and it is very suitable for low computation power equipment.