Optical feedback self-mixing interferometry is an emerging sensing and measurement technique, which is quite different with traditional double-beam interferometry. To perform precision vibration measurement under the condition of moderate optical feedback, a vibration measurement method is proposed based on moderate optical feedback self-mixing interference. Based on the analysis of the optical feedback self-mixing interference signal fringes, it is found that saw-like fringes in the self-mixing signal waveforms can be observed by properly choosing the optical feedback level and line width enhancement factor of semiconductor laser. With the saw-like fringe not only the vibration amplitude can be measured, but the movement direction can also be determined. The proposed measurement is based on the analysis of saw-like fringes with the following two steps. Firstly, rough measurement of displacement is carried out by counting the fringe numbers with the resolution of half wavelength. Then based on the studies of fractional fringe structure under modulate optical feedback, a linear formula for displacement within half wavelength is derived, and precise displacement measurement is realized. Computer simulations show that the proposed technology is able to achieve high-resolution and large-range measurement of vibration amplitude.