The invention discloses machining technology of a titanium alloy lightweight reinforced airfoil. The machining technology of the titanium alloy lightweight reinforced airfoil comprises the following steps that material preparing, feeding, sheet metal forming; cleaning; welding isolation agent coating, soldering and sealing, airtightness detecting, mold filling and superplastic forming/diffusion connection are carried out, specifically, a mold is placed in superplastic forming equipment, and the airfoil is subjected to vacuum pumping by 10<-2>10<-5>Pa, temperature is raised to 870-940 DEG C, pressurization of an outer layer air inlet is 1.2-1.5 MPa, heat preservation is carried out for 2-4H, superplastic forming of upper and lower cover plates is achieved, diffusion connection exists between an upper grid and an upper core plate, a lower grid and a lower core plate, the upper and lower core plates, pressurization of an inner air inlet 1-1.5 MPa, heat preservation is carried out for 2-4H, superplastic forming of the upper and lower core plates is achieved, a superplastic formed structure of the upper core plate is in diffusion connection with the upper grid and the upper cover plateseparately, a superplastic formed structure of the lower core plate is in diffusion connection with the lower grid and the lower cover plate separately, and furnace cooling is carried out; and finishing and polishing are carried out.