In order to improve the efficiency of quantum secure transmission, the properties of n-particle Greenberger-Horne-Zeilinger(GHZ) state were used to study the quantum secure direct communication (QSDC) with single photon mixture. The implementation process of communication was designed. The transmission efficiency, quantum bit utilization, and coding capacity of communication were discussed, and its security was theoretically analyzed. Compared with other classical QSDC protocols, the results show that the coding capacity and the transmission efficiency can be respectively improved to (n+1)bit and 200% with this scheme. Security analysis shows that the protocol can resist interception and measurement retransmission attacks, Trojan horse attacks, denial of service attacks, auxiliary particle attacks and entanglement attacks.