The invention provides a blind hole floating grinding method and device. The blind hole floating grinding method and device combine the characteristic of floating of a grinding rod hanging in the air in an actual manual grinding process and the characteristic of durability of a honing stone. The blind hole floating grinding method is characterized in that a structural component with a blind hole is clamped by selecting and using a floating device with a floating function and is arranged on a working table of mechanical equipment; meanwhile, an interchangeable adjustable grinding bar is clamped on a main shaft of the equipment; the working part of the grinding bar adopts the honing stone, thereby effectively prolonging the service life of the grinding bar; and the machining process of upper rotation plus lower floating is realized by reasonably setting a variable stroke path, and the blind hole of the structural component is subjected to floating grinding machining. The blind hole floating grinding method and device have the beneficial effects that the technical difficulty of ultimately realizing the machining process of upper rotation plus lower floating by combining manual grinding and the honing stone is broken through; the obtained structural component with the blind hole has high precision and high surface roughness value; and the device is convenient and simple to use and operate; the machining cost and efficiency of the structural component product are effectively improved; and the beneficial effects of shortening a production cycle and improving the quality of the structural component product are achieved.