The fomula of insertion loss and isolation of polar izati on - indePendent walk - off optical isolator are presented theoretically by Jones Matrix in this paper. The influcences of polarization beam-splitter , Faraday rotator and half-wave plate on insertion loss and isolation are discussed. The experiments of the optica1 isolator developed by the authors show that the fiber to fiber insertion loss was 1. 46 dB and isolation was 34 dB and with size of 13 ×10 ×46 mm3.