In this paper,an optical feedback system based on fiber linear lasers is presented.The effects of optical feedback could be equivalent to the variation of laser cavity loss,and the output expression of the optical feedback system is deduced.A model is built to analyze the feedback influence on the system.The internal optical feedback effect on fiber linear lasers is similar to self-mixing interference,and the former has same phase sensitivity with the later.The influence from different parameters is analyzed in simulation.The system output is detected in experiment,and the influence of different parameters is also discussed by changing the experimental conditions.The experimental results show a good agreement with the simulated results.The conclusion can be summarized as follows:One fringe shifting of the system output corresponds to a target displacement of λ/2; the different inclination refers to different movement direction; the better sensitivity of optical feedback system can be obtained by choosing appropriate feedback cavity length and target reflectivity.Consequently,this system can be applied to optical survey,such as displacement,distance,velocity measurement,etc.