Multi-dimensional network structure of filler is critical to the properties of supercritical CO2 (scCO2) foamed materials, and micro-/nano- fillers have different 3D network structures in a confined space. In our study, confocal laser scanning microscopy, a powerful technique for material 3D structure characterization, is then successfully applied for the first time to construct the multi-dimensional (including 2D and 3D) foam structure and the 3D network structure of silicon carbide whiskers (SiCw) obtained in scCO2 foaming by artificial design of double fluorescence structure of composite polymeric foams. Fluorescent SiCw were successfully prepared by using fluorescence grafting method. Besides, micro-/nano-cellular foam models and fiber network structure models were also constructed by using simulation method. By analyzing the foam structure and foam models, it was found that the statistical cell size via 2D characterization is only 0.79 of that via 3D characterization, the statistical cell density via 2D characterization is 1.2 of that via 3D characterization; By analyzing the fiber structure and fiber models, it was found that the real fiber length was decreased during the sample preparation process and the shortest distance between fibers was also decreased as the filler contend increased.