Abstract: After the deep-cavity shell parts made by carbon-fiber reinforced composite material is formed, the parts will wrap the forming mould tight for cooling shrinkage. Then the problems of difficult releasing and easy distortion come into being. According to the feature of carbon-fiber reinforced composite material, a kind of forming mould with sectional cone structures has been designed, which has solved the problem mentioned above. The mould is released simply and reliably by disassembling the modules with mould releasing tools. QT-500, which has the feature of good machining and stable dimension, is used to make the mould. QT-500 also has the approximate coefficient of expansion with the carbon-fiber reinforced composite material. The formed parts with high precision have smooth surfaces and stable dimensions. The mould solves the difficult problem of mould releasing for deep-cavity shell parts and also provides a new design method for manufacturing the parts of the same kind.