Principles of stimulated Brillouin scattering (SBS) and microwave photonics(MWP) system based on Brillouin processing (BP) in optical fiber are summarized. Based on Brillouin-selective amplification (BSA) and Brillouin-selective suppression (BSS), some applications of BP are deeply analyzed, such as optical generation of microwave signals, photonic frequency upconversion/downconversion and frequency multiplication of microwave signals, MWP complex-valued coefficients and single response filter, MWP phase shifter, and link performance improvement in radio-over-fiber (RoF) system. Advantages and disadvantages of BP in these applications are discussed, and some potential improvement projects are presented. Development trends and application prospects of BP in MWP and integrated microwave photonics (IMWP) are discussed.