The utility model provides a four sides letter square board anchor clamps for vibration testing, these anchor clamps include the base, adjustable retaining member and layering, the base includes that relative setting that the rigid coupling becomes square frame is before, a back brace channel -section steel and a left side, the channel -section steel is propped on the right side, it is preceding, be equipped with between the back brace channel -section steel before with, equally spaced horizontal muscle between the back brace channel -section steel, perpendicular equidistance is equipped with two vertical muscle on the horizontal muscle, it is preceding, a back brace channel -section steel and a left side, the channel -section steel upper surface two sets of isometric adjustable lockings of parallel arrangement strip is respectively propped on the right side, adjustable locking strip is inboard high recess such as to be equipped with, be equipped with the layering in the recess. This anchor clamps rigidity is big, and clamping -force is big, will vibrate the motion of mesa and transmit square board undistortedly in vibration testing.