Abstract: Molybdenum and molybdenum alloys are key high-temperature resistant materials in fields such as nuclear power. However, the welded joints exhibit problems such as high brittleness, low strength, and oxidation tendency, which often results in defects like porosity and cracks. To address the problems of porosity, cracks and embrittlement in high-performance molybdenum and molybdenum alloy welds, the causes of porosity and cracks in joints under various welding methods were reviewed in detail, including tungsten inert gas welding (TIG), electron beam welding (EBW), laser beam welding (LBW), friction welding and diffusion bonding. It also introduced measures to improve the performance of molybdenum alloy welded joints from different welding methods, such as adjusting the welding process and alloying method, etc. It can provide a reference for the selection of welding methods for molybdenum and molybdenum alloys.