Abstract: In sensor information collecting system of wisdom agriculture，considering ability of anti-interference of system，output signal of the sensor and collection system do not share the ground.This requires a isolation amplifier，it can transmit output signal of sensor to collection system without distortion.Therefor，two isolation amplifiers was designed with high-linearity analog optocouplers HCNR200，they could isolate unipolar voltage and bipolar voltage respectively.Method of calculating circuit parameters according to different input voltage was explained in detail，and the corresponding circuit diagram was given.Finally，correctness and feasibility of designed circuit was verified by experiments.