This paper is concerned with the speed regulation of permanent magnet synchronous motor systems using sliding mode control. To deal with the contradiction between reaching speed and chattering while ensuring finite time convergence, a new sliding mode reaching law is designed by introducing a variable gain associated with system states. Based on this, a speed regulation controller is first designed for permanent magnet synchronous motor systems using the new reaching law to solve the speed regulation problem and improve system robustness. A rigorously theoretical proof is provided for the designed speed controller using our proposed practical finite time stability criterion. We further investigate the speed estimation of permanent magnet synchronous motors without mechanical sensors. To obtain more accurate rotor information, a new sliding mode observer is designed by incorporating a back electromotive force observer, whose validity is verified by Lyapunov theory. Finally, the correctness of our developed theory is verified through simulation studies.