High-resolution optical signal processing is highly required in various Frontier fields such as high-speed optical communication systems, microwave photonics systems and high-resolution optical computing. The fundamental functions are high-resolution control on optical spectrum, microwave spectrum and time-domain waveforms. High-resolution programmable optical filter is the best choice to realize the above functions, because it can directly control the optical spectrum by programmable optical filtering, control the microwave spectrum by flexibly filtering the microwave modulated optical spectrum, and control the waveform shape by frequency-manipulating combined with time-frequency mapping. Therefore,high-resolution programmable optical filter is the key instrument in optical signal processing fields. In this article, we review the implementation methods of different programmable optical filters, and specially introduce the research progress and key technologies of stimulated Brillouin scattering based high-resolution programmable optical filter.