The Sensor and Circuit of testing fabric infiltrate characteristic are designed. By testing capacitance variation ΔC between the sensor and two plates. It can detect the spread of area of the fabric seepage ΔS and determine the seepage rate of the tested fabric. The Calibration testing has been achieved for the Sensor and Circuit. The data is given out. The linear distortion of the testing Sensor and Circuit is smaller than 5%.It can meet the technical requirements of the testing seepage characteristics of textile products.