Length measurement device with high precision and application method thereof

The present invention discloses a length measurement device with high precision and an application method thereof. The length measurement device comprises a fixed housing, the inner cylinder of the fixed housing is movably connected with a rotation shaft base, a main dial is coaxially arranged at one end face of the rotation shaft base, main scales are distributed on the main dial on the circumference, there is one main scale division unit between each two adjacent main scales; and a rotation shaft I and a rotation shaft II are coaxially arranged at the other end face of the rotation shaft base in order; the rotation shaft I is in threaded connection with the inner cylinder of a sleeve cylinder I, the outer cylinder wall of the sleeve cylinder I is provided with a rib I, and the rib I is in sliding connection with a groove I arranged at the inner cylinder wall of the fixed housing; the rotation shaft II is in threaded connection with the inner cylinder of a sleeve cylinder II, the outer cylinder wall of the s