The dispersion property of the optical glass sensing head and its effect upon the sensitivity of a bulk-glass optical current transformer were theoretically analyzed by taking the Jones′ Matrix as a mathematical tool, simulated with a computer and verified with an experiment. In an optical current sensing system,when the fluctuations of the driving current or the ambient temperature of the optical source occurs, the peak wavelength of the source would change.It would result in the fluctuation of the sensitivity of the system because of the existing of the dispersions of the reflection-induced retardance,Verdet constant and the linear birefringence inside the sensing head.The investigation results showd that the dispersions would obviously affect the scale factor of the system.Therefore,it was necessary to stabilize the driving current and the ambient temperature of the optical source by some technical means.These results might be useful for the researchers and designers who works in the optical current sensin