Abstract: In this paper we first introduce the basic principle, experimental schemes and results of buffer-gas cooling for molecules, and recent research progress. We then present the basic principle, technical schemes and experimental results of velocity filtering to generate cold molecular beams, including Stark velocity filtering, Zeeman velocity filtering and all optical velocity filtering schemes based on electrostatic, electromagnetic and optical bent guiding technologies. Some important applications of cold molecules at a temperature of about 1K produced by buffer-gas cooling and velocity filtering are briefly introduced in the final section.