With continuous improvements of semiconductor laser performance and semiconductor laser technology, diode laser has been adopted in many applications in research and industrial areas, such as optical frequency standard, fiber communication, laser ranging, high resolution spectroscopy, laser cooling and trapping atoms, etc. Frequency stability and line width are the most important parameters concerned in special applications. In this paper, based on saturated absorption spectroscopy, we introduce the frequency stabilization of diode laser by metastable Kr atom. For its narrow natural line width, Kr transition can be used as a perfect frequency reference for laser frequency stabilization, and the reproducibility can also easily be achieved because of the intrinsic physical property. The laser frequency can also be shifted by an acoustic-optical modulator by precisely adjusting its driving frequency. This is important as one tries to manipulate different isotopes via the same laser. Methods of measuring frequency stability and line-width are also discussed at last.