Carbon fiber composite core has a strong axial tensile capacity， while the properties of radial shear resistance， compressive capacity and splitting resistance are weak. In the process of line construction， such as wire crimping and conductor clamping by grip jaw， radial pressure failure is easy to occur， which may cause security risks in transmission line construction and safe operation. At present， there is little research on the radial pressure of carbon fiber composite core. The radial pressure tests of carbon fiber composite core of different diameters are carried out to get the failure pressure of carbon fiber composite core test samples. With ABAQUS software the radial pressure simulation model is established. According to the failure pressure data of carbon fiber composite core in the radial pressure test， the vertical radial force is applied to the pressure block. The radial pressure maximum value of carbon fiber composite core of different diameter is obtained by numerical calculation of finite element software. The results show that the situation of failure of carbon fiber composite core is the outermost glass fiber layer flattened causing the test sample to split integrally. The radial compressive allowable stress of carbon fiber composite core with different diameters increases with the increase of the diameter. The research results provide a reference for the design and application of construction machines and tools for carbon fiber composite core of transmission line.