Abstract: By using glass fiber 120 twill fabric/epoxy 5224 as the panel and Nomex honeycomb as the core，the ability of resisting the lateral distortion of honeycomb cores was investigated. For cocuring process with the vacuum bag，a gas pressure measuring method was established and was used to study the influence factors of core internal pressure and the relationship between core internal pressure and core crush. It is found that the ability of the honeycomb core to avoid core crush is limited，especially for large core grid length and core thickness. Core internal pressure has close relation with the expansion of core gas and permeability of prepreg stack，so core internal pressure is affected significantly by the temperature cycle，the number of prepreg plies and adhesive film. Moreover，the core internal pressure plays an important role in avoiding core crush. Larger internal core pressure before prepreg gelation is helpful to preventing core crush.