A new scheme of quantum key distribution (QKD) using frequency and time coding is proposed,in which the security is based on the frequency-time uncertainty relation.In this scheme,the binary information sequence is encoded randomly on either the central frequency or the time delay of the optical pulse at the sender.The central frequency of the single photon pulse is set as ω1 for bit 0 and set as ω2 for bit 1 when frequency coding is selected.However,the single photon pulse is not delayed for bit 0 and is delayed in T for 1 when time coding is selected.At the receiver,either the frequency or the time delay of the pulse is measured randomly,and the final key is obtained after basis comparison,data reconciliation and privacy amplification.With the proposed method,the effect of the noise in the fiber channel and environment on the QKD system can be reduced effectively.