Abstract: The automatic system developed by us is discussed for the fluorescent magnetic inspection of some steely axle-like workpieces. The system has following advantages: The flourescent digital image that has the large signal-to-noise ratio could be sampled. Only if the grey-scale gradients for each image point are calculated, can the image segmemtation on a fast adaptive dynamic thresholding algorithm be achieved. The two-valued image is effectively processed by mathematical morphological expansion operation, the contraction operation based on the copulating number, and the filtration operation. And it is testified that the image acquisition and processing with this automatic system are practically useful.