The utility model provides a railway tunnel boundary limit image processing system, include: wait to detect tunnel information acquisition unit, mileage record unit, image acquisition memory cell, image processing unit, the long -pending calculating unit of tunnel section. This method includes: be written into and wait to detect tunnel information, set for initial mileage to detect the garage in the tunnel and advance the in -process to mileage accumulative total, with the speed collecting of 25 frame / seconds and preserve laser light belt image, it obtains complete tunnel section image to carry out the geometric transformation, go making an uproar correction, image interpolation, mosaicing processing to laser light belt image. It is long -pending according to tunnel section calculating image tunnel section. The utility model discloses a system accomplishes the real -time collection and the storage of tunnel section information to the image processing and the file of tunnel section information carry out. Effectively get rid of the noise in the laser light belt image, obtain complete laser area image.