The self-mixing model are changed when changes of both light intensity of the optical beam which is reflected or scattered and the nonlinear of the system,then makes the change of signal waveform.All of these make signal processing rather challenging.In this paper,a new behavioral model of weak optical feedback based on orcad10.5 of cadence is proposed to represent the optical feedback self-mixing phenomenon and to simplify the solution of nonlinear equations involved in this problem.At the same time,it not only established an behavior model of the optical feedback sensor based on weak feedback and built a platform to combine hardware and software,but also develop new methods for signal processing of target measurements such as displacement,velocity and distance measurements.