A quantum secure direct communication and authentication protocol is proposed by using single photons.An information transmission is completed by sending photons once in quantum channel,which improves the efficiency without losing the security.The protocol encodes identity-string of the receiver as single photons sequence,which acts as detection sequence and implements authentication.Before secret message is encoded as single photons sequence,it is encrypted with identity-string of the sender by using XOR operation,which defends quantum teleportation attack efficiently.The base identity-strings of the sender and the receiver are reused unconditionally secure even in noisy channel.Compared with the protocol proposed by Wang et al.(Phys Lett A,2006,358:256–258),the protocol in this study sends photons once in one transmission and defends most attacks including‘man-in-the-middle’attack and quantum teleportation attack efficiently. A quantum secure direct communication and authentication protocol is proposed by using single photons. An information transmission is completed by sending photons once in a quantum channel, which improves the efficiency without losing the security. The protocol encodes identity-string of the receiver as single photons sequence , which acts as a detection sequence and implements authentication.Before secret message is encoded as single photons sequence, it is encrypted with identity-string of the sender by using XOR operation, which defends quantum teleportation efficiently efficiently. The base identity-strings of the sender and the receiver are reused unconditionally secure even in noisy channel. Compared with the protocol proposed by Wang et al. (Phys Lett A, 2006, 358: 256-258), the protocol in this study sends photons once in one transmission and defends most attacks including’man-in-the-middle’attack and quantum teleportation efficiently efficiently.