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• SiCN honeycomb ceramic is prepared from 3D printed photocurable polysilazane. • The optimal composition of acrylate and polysilazane affords high-strength ceramic. • Combination of acrylate and polysilazane results in high-content free carbon. • SiCN honeycomb ceramic has excellent intrinsic microwave-absorbing property. The combination of 3D printing technology and polymer-derived ceramic route provides an attractive strategy to construct microwave-absorbing honeycomb with fine structure through flexible process. However, preparation of honeycomb ceramics with both excellent mechanical and microwave-absorbing properties is still challenging. Herein, SiCN honeycomb ceramic was fabricated by stereolithography from UV curable polymeric precursor consisting of polysilazane and multifunctional acrylates. By optimizing the multifunctional acrylates and its ratio, the decomposition of organic moiety and the ceramization process of precursor are matched, rendering the achieved ceramic with high compactness. The hardness and specific compressive strength of SiCN honeycomb ceramic reach as high as 14.3 GPa and 333.3 MPa/(g·cm3), respectively. Meanwhile, at low pyrolysis temperature, the copolymerized acrylate and polysilazane that formed during curing process was converted to free-carbon nanodamins in-situ, which endows SiCN honeycomb ceramic with the minimum reflection loss of –49.0 dB, namely microwave absorption rate over 99.99%. [ABSTRACT FROM AUTHOR]