Accuracy and stability are the main performance indexes of optical current transducer（OCT）. Based on adaptive OCT a new method which combines a new high stable sensor with the lock-in amplifier for weak photoelectric signal detection is proposed in the paper. The long-term operation stability of OCT is improved by using optical structure of solenoid collecting magnetic field in magneto-optic sensors and shortening the length of magneto-optical materials. The steady and transient metering accuracy is improved by combining OCT with traditional current transducer and adopting lock-in amplifier in signal processing system. Finally， The signal processing system is verified by simulation on virtual instrument platform LabVIEW.