With the increasing in the use of composite structures in aircraft structural components, the parts are becoming larger and more complex, and are gradually being used in the main load-bearing components, which puts higher requirements on the forming quality of composite structures. Firstly this article elaborated on the characteristics of the autoclave for composite structures, and introduced the heat curing forming processes such as co-curing, co-bonding, and secondary bonding. Secondly, based on the characteristics of temperature changes in the autoclave forming process, the selection of mold materials and thermal expansion compensation methods in the composite forming process were introduced. Finally, taking the most commonly used frame type mold as the object, the general guidelines for composite forming mold design were provided, and the key elements of composite forming mold design were discussed to make the mold structure more conform to the forming requirements of composite parts, providing a reference basis for the forming and manufacturing of composite parts in the aviation manufacturing industry.