An automatic method of measuring optical fiber geometric parameters is described. The end face of the fiber is imaged by a microscope and recorded by a CCD camera, and then the image is transferred to a image grabber plugged in a microcomputer for further analysis. Several digital image processing methods are used to remove the noise in fiber image. The image segment algorithm is used to extract feature datapoints. The data is analyzed by using different algorithms to give the geometry parameters of the fiber. Sophisticated software is programmed. An instrument developed based on the hardware and software described above can be operated conveniently with high accuracy.