The invention discloses a protection device for installation of a soil body filling inclinometer to solve the technical problem through the technical scheme. According to the technical scheme, the protection device is composed of steel protection plates, angle steel supporting frames,connecting rings, thread steel ejector rods and connecting bolts. Specifically, an outer frame is composed of the protection plates; the angle steel is arranged at the four corners of the upper end and the lower end of the outer frame and is formed by steel bars which are staggered vertically in the height direction, wherein one ends of the steel bars are welded to the connected protection plates, and the other ends of the steel bars forming the angle steel are connected through steel rings and the bolts provided with the steel rings in a matched mode; the upper ends and the lower ends of the protection plates are provided with angle steel supporting frames corresponding to the angle steel; the opposite angle steel supporting frames are fixedly provided with the thread steel ejector rods; the inclinometer is arranged in the center of the outer frame. The invention further provides a machining method and a use method of the protection device.