The utility model discloses a special milling cutter of impact specimen U type breach, including annular cutter body, evenly distributed has a continuous arc sword tooth on the outer circumference of cutter body, the tip cross -section of sword tooth is the U -shaped structure, and the width of U -shaped structure is 2mm, and U -shaped structure top curvature radius is 1mm, the U -shaped structure highly be greater than 5mm, the root width of sword tooth is greater than the width of U -shaped structure, is equipped with the step transition between root and U -shaped structure. The utility model provides a special milling cutter installs on the output shaft of milling machine and the fastening, rotatory and process impact specimen along with the output shaft then, and the degree of depth h of U type breach can realize through the control milling machine depth of cut, and U type notch size that processing was come out accords with the summer and than collision test's requirement, not only satisfies the processing of two kinds of different degree of depth U type breachs, can also practice thrift the cost, improves machining efficiency.