Two-dimensional metal-organic framework nanosheets （MONs） are a type of 2D porous materials that have received extensive attention in recent years. With ultra-thin thickness， abundant accessible unsaturated coordination sites， large specific surface area， advantages of adjustable structure， etc.， MONs are widely applied in many fields such as separation， conduction， sensing， and catalysis. This article mainly reviews the preparation， characterization and application in heterogeneous catalysis of MONs in recent years. The preparation of MONs includes two strategies， namely top-down and bottom-up. The top-down strategy is simple to operate， mainly involves exfoliation of layered bulk MOFs through physical or chemical means to into MONs. The bottom-up strategy involves direct assembly of 2D MONs from metal ions and organic linkers under controlled experimental conditions. The characterization methods and techniques of MONs are discussed from the aspects of structure composition， microscopic morphology， and macroscopic properties. In addition， the application of MONs in heterogeneous catalysis， mainly organic conversion， is introduced， including catalytic oxidation reaction， Knoevenagel reaction， CO₂ cycloaddition reaction， hydrogenation reaction， etc. Finally， the opportunities and challenges in the field of MONs are pointed out.