Adaptive observer method is a widely used method, which includes a reference model and adjustable contained identification parameters. Its speed adaptive law is derived by Popov ultra-stability theory, which ensures the asymptotic convergence of the parameter estimates, and it has a good dynamic performance. The control system using space vector control method, and the implementation process of vector control on permanent magnet linear synchronous motor is analyzed particularly, we also give the modules of control system in Matlab/Simulink. Through the results, we can verify the reliability of the speed sensorless control method. The problem of instability in the low-speed electric mode according to the observer linearization method was analyzed. To solve the problem, the observer augmented with a signal injection technique was researched. The simulation results show that the method is effective to enhance the system parameter robustness and speed observation, improve low-speed performance of the speed-sensorless vector control system.