The invention discloses a quantum key distribution method based on single photon superdense coding. The method comprises the following steps that a party A prepares a photon state which is randomly inan R ground state, carries out deflection operation on the photon state and then sends the photon state to a party B; the party B carries out the deflection operation on the photon state again and then returns the photon state to the party A; the party A compares a measured quantum state with originally prepared quantum state and sends a comparison result to the B party; the party A judges whether employed measurement basis is accurate or not, carries out marking if the employed measurement basis is accurate, sends marked location information to the party B and discards wrong location information; and the party A and the party B generate a shared bit string according to own information and received information. Compared with an entangled state QDKD (Quantum Dense Key Distribution) protocol, the method has the advantages that complex quantum resources and equipment are avoided, and the method is more economic and feasible.