To detect the laser doppler signal, the unknown signal is tracked by the known signal using the concept of topological contravariance. The unknown topological space U and known space M are founded, and then the unknown signal’s transformation is tracked dynamically according to this mapping relationship between the two spaces. The system equation is obtained by gradient-descent method, and the conditions of stability are given by Poincaré mapping. The proposed method is applied to measure the in-plane displacement signal of the solid 50 m away using laser doppler, signal. The result proves that the method can detect laser doppler. signal accurately, its relative error is less than 0.7%. This work has been supported by the National Natural Science Foundation of China (No. 60704037).