The invention discloses a gradual change spiral groove cycloid milling cutter for titanium alloy machining and a grinding method thereof. A milling cutter body comprises a cutter handle portion and acutting edge portion, the cutting edge portion comprises a cycloid blade portion and a peripheral blade portion, the cycloid blade portion includes two cycloid blades which are identical in structureand are symmetrically distributed, the two cycloid blades are connected at the position of the cutting edge portion, the peripheral blade portion comprises two peripheral blades which are identical instructure and are symmetrically distributed, and the peripheral blades are smoothly connected with the ends, close to the cutter handle portion, of the cycloid blades; and the peripheral blades are arranged between the cycloid blade portion and the cutter handle portion, two center grooves are formed between the two cycloid blades, two symmetrical gradual change spiral grooves are formed betweenthe peripheral blades, and the gradual change spiral grooves are connected with the corresponding center grooves. By means of the milling cutter, after the grinding method is used for processing, thematerial removal rate is improved during work, the residual height of the processed surface is lower, the surface quality is better, the cutting force borne per unit area is small, cutter wear is reduced, and the service life of the cutter is prolonged.