We have studied a function-lock strategy for all-optical logic gate (AOLG) utilizing the cross-polarization modulation (CPM) effect in a semiconductor optical amplifier (SOA). By monitoring the power of logic light, the strategy realized controllable methods to capture OR and NOR functions and switch between them. The strategy has been successfully applied in experiment with 10-Gb/s not-return-to-zero (NRZ) signals, which has a high success-rate above 95% and ensures the high extinction ratio of result light above 11.4 dB. Every step in the strategy has definite numeric evaluation, which provides the potential of automatic implementation.