A 1.1km long all-fiber quantum key distribution experimental setup has been realized for the first time at 850nm. The system employs the BB84 protocol to establish a secret key between two parties, the security of which is guaranteed by Heisenberg's uncertainty relationship and the quantum noncloning principle. Phase modulated single photons are used to carry the key. The effective transmission rate is 3 bit/s, with a bit error rate of 9%.