An all-optical thresholder based on the nonlinear optical loop mirror (NOLM) and the self-phase modulation (SPM) of photonic crystal fibers (PCF) which can be used in photonic neuron is achieved. The nonlinear coefficient of PCF is 16.98 (W·km)-1, while a tunable isolator into the NOLM is also introduced. Due to the use of highly nonlinear PCF and tunable isolator, it requires shorter cavity length and lower input power. By using the alloptical thresholder, optical signal extinction ratio can improve more than 6 dB. All devices in the all-optical threshoder are passive, therefore it is good for high speed optical signals. The all-optical thresholder also has broad application for other optical communication systems.