All-optical packet clock recovery is a key technique for high-speed optical packet switching(OPS) networks. The locking and unlocking time of the packet clock determines the guard time in the OPS, and therefore affects the network bandwidth utilization. An all-optical packet clock recovery system with ultrafast locking and unlocking time via the self-phase modulation effect of the saturated semiconductor optical amplifier(SOA) and an optical band-pass filter was proposed. The 10 GHz packet clock recovery with locking time of two code-periods and unlocking time of six-code periods is obtained.