Light-weight and exceptional microwave absorption are two vital characteristics for microwave absorbers in practical applications, but still face challenges. Herein, we employ a sacrificial template strategy to fabricate heteroatoms-doped carbon nanocages (CNs) via chemical vapor deposition, in which heteroatoms are simultaneously doped into the carbon frameworks by bubbling flowing source liquid. Compared with CNs, doped heteroatoms, accompanied with the inevitably defective arrangements in the lattice, not only decrease the electrical conductivity and balance the impedance characteristics, but also introduce structural-chemical defects and trigger dominant dipolar/defect polarization. As a result, both the minimum reflection loss (R_L,min) and effective absorption bandwidth (EAB) greatly increase at an ultralow filler loading of 5 wt.% owing to internal hollow void and high specific surface area. The R_L,min values reach −53.6, −43.2, and −50.1 dB for N-CNs, S-CNs, and N,S-CNs with the corresponding EAB of 4.9, 2.5, and 3.1 GHz, respectively. Furthermore, this work provides an effective strategy for the construction of heteroatoms-doped hollow carbon frameworks in large-scale production and the obtained doped carbon nanocages can be used as light-weight and high-performance microwave absorbers.