An autoclave molding strategy in the preparation of a large-size， thick-wall， special-shaped composite tubular support was described， in which the mold design， lay-up process and molding pressure were optimized. Based on the dimensions and quality requirements of the product， a set of split molds with designed dimensions was used. In the lay-up process， the disconnect way of the carbon fiber was designed. Last， in the curing process， a cycling gradient pressure was applied， the pressure at different temperature and the maximum pressure were controlled. The results show that these methods effectively guaranteed the molding pressure of the support. The surface of the prepared support is smooth， and there are no defects such as delamination， porosity and so on. In addition， the dimensional accuracy， content of resin meet the user’s requirements.