Optical pulse trains from mode-locked lasers carry low-jitter microwave signals.High-quality microwave signal could be obtained by using a band-pass filter.A regeneratively mode-locked fiber laser is used as an oscillation source to generate high-quality microwave signal.The phase-locked technology and cavity length control guarantee the stability of the system.The cost of the system is dramatically reduced by using the structure of "single-mode fiber+Farady rotator mirror" instead of polarization-maintaining structure.A semiconductor optical amplifier(SOA) is introduced into the optical microwave loop,which improves the side-mode suppression ratio effectively.The generated 20 GHz microwave signal has great performance with phase noise of-98 dBc/Hz at 10 kHz and line-width less than 5 Hz.The frequency stability is better than 1×10-10 within 10 h observation.