Abstract: The fiber optic current transformer is a system that comprises parameter uncertainty and noise signals. For improving precision of the system, the design of robust H -infinite controller was discussed. The fiber optic current transformer based on closed-loop detection was analyzed, and the model of the system was built. The design problem of the fiber optic current transformer controller was considered which guaranteed that the closed loop system was asymptotically stable and the noise suppression of the system was improved. The controller was proved that the control system meets the design target. Then the problem of the design of the robust controller can be solved on the basis of linear matrix inequality technique. The result was provided to show the effectiveness and feasibility of the robust controller by the computer-s simulation and experimental test.