An infrared optical fiber evanescent wave sensor for on-line and accurate detection of vinylidene chloride in water is fabricated in this work, The sensor is composed of a U-shaped mid-infrared optical fiber sensing probe, a vinylidene chloride selective sensitive membrane and a superhydrophobic membrane, The tetrafluoroethylene sensitive membrane was coated on the surface of the U-shaped area, and the superhydrophobic membrane was coated on the surface of the vinylidene chloride sensitive membrane, The U-shaped sensing region can enhance the intensity of the evanescent wave on the surface of the optical fiber, thereby improving the sensitivity of the sensor, The sensitive membrane can selectively detect the vinylidene chloride in water and improve the accuracy of the measurement results of the sensor, The superhydrophobic membrane can eliminate the negative influence of the water molecules on the measurement results, The characteristic absorption spectrum of vinylidene chloride, the response sensitivity, response time and selectivity of the sensor to the vinylidene chloride are studied experimentally, A theoretical model for measuring the vinylidene chloride by sensor is established, The results show that the sensor has high selective sensitivity to vinylidene chloride, the sensitivity is up to 0, 002 1 abs/(mg·L-1)) and the response time is 230 s,