Abstract: Fiber optic sensor has been proved a very promising monitoring method in many fields such as arms and aerospace industry. One of its most popular applications is the cure process monitoring of advanced fiber reinforced resin matrix composite. The main obstacle of wide utilization of this technique is the high cost and complex modulation technology. A novel fiber optic sensor was developed, which has the feature of high sensitivity and low cost and is easy to handle, to do the job. The fiber optic sensor is developed based on fiber optic microbend losses and aimed to monitor the pressure variation, through which key information to the cure can be obtained through computation directly or indirectly, on the reinforced fiber network during the cure process. In this presentation, the design and preparation of the sensor is given. The dynamic and static response of the fiber optic pressure sensor under pressure is tested. The influence of the temperature and refractive index variation around the sensor on the response of the sensor's signal attenuation is dicussed. On the basis of the fiber optic pressure sensor, a portable instrument is integarted, which includes laser diode, detector, A/D, etc. With it in-situ monitoring of the cure process of fiber reinforced composite laminates is carried out and good result is obtained.