Gives an approach for long-distance isolately transportating analog signals in high-power systems such as magnetically levitated systems,in which the control system is detached from the controlled objects . As the core of the approach,the circuits of voltage-to-frequency and frequencyto-voltage were built with AD650 to convert signals ,which were long-distance isolately transpotated through fibreoptical,and the circuits of voltage-to-frequency was shielded.The circuits structure were designed, and the method how to calculate the circuits parameters was gived. It was proved by theoretical analysis and experiments on power converter that the designed approach is effective for long-distancely transportating analog signals. The delay of output signals caused by transportation may be controlled below 20µs and the frequency of input signals may be up to 5kHz.