Effectively filtering out noise and improving the signal-to-noise ratio (SNR) and measurement accuracy is essential in signal processing for optical current transducers (OCT). This paper introduces the principle and SNR characteristics of OCT which is based on the Faraday Magneto-optic effect, and proposes a particle filtering method to address the problem of low SNR of OCT. In the verification on the simulation platform of MATLAB, a particle filtering dynamic model is established and a fission bootstrap particle filter (FBPF) algorithm with proper parameters is implemented, for direct current and alternative current respectively. The results indicate that the proposed method effectively improves SNR and measurement accuracy.