To solve the problem of secure location service, this paper proposes a range-free secure localization protocol—ServLoc localization protocol. By means of authenticating messages, hidden actors passively receiving localization requests and filtering false location reports, etc, ServLoc localization protocol can defend location attacks, keep location in privacy and locate sensor node in a distributive way. In addition, this paper also proposes a voting-based location verification scheme—ServLoc verification protocol and ways to defend actor attacks. The analysis illustrates that ServLoc verification protocol can trade off the security and effective localization problem of WSAN. ServLoc scheme can also effectively provide secure location service, even if the WSANs suffer location attacks.