Three-dimensional carbon-based materials have attracted much attention for electromagnetic wave absorption because low-dimensional materials have failed to meet the needs of constructing effective networks with ultra-light properties due to their easy agglomeration and in-plane stacking. The 3D element of quadrangular cone carbon was innovatively applied in this work to construct interconnected networks (MFC). This material successfully overcomes the disadvantages of easy agglomeration and in-plane stacking in low-dimensional elements, allowing for more efficient construction of absorbing networks. The prepared MFC exhibits excellent EAB (6.70 GHz) and RL (-50.92 dB), especially at an ultra-low filling ratio (1.04 wt%). Such superior performance can be attributed to the MFC effective network constructed by quadrangular cone carbon facilitating the entrance and diffuse scattering of electromagnetic waves. This study may provide new inspiration for constructing an effective absorbing network of pure carbon with 3D elements (quadrangular cone carbon), realizing ultra-low filling and broadband microwave performance.