Abstract: In order to regenerate HCHO adsorption, both types of sepiolite stirred at 15% HCl for 8.5 h or heated at 100~600 ℃ for 5 h were applied to static adsorption experiments in high concentration HCHO to research the HCHO adsorption effects, and X-ray diffraction, infrared adsorption spectroscopy, thermogravimetry, BET specific surface area analysis and scanning electronic microscopy were adopted to research the adsorption mechanisms. The results revealed that the sepiolite heated at ≤450 ℃ held favorable HCHO adsorption capacities, while those modified by acid or heated at ≥500 ℃ had significantly reduced HCHO adsorption capacities. It is inferred that the crystalliferous water in sepiolite could chemically absorb HCHO and the structural microhole, basically composed of zeolite holes, could be occupied by HCHO through physical adsorption. Subjected to acid modification, large part of Al³⁺ and Mg²⁺ in the sepiolite structure were replaced by H⁺, then the crystalliferous water bonded with Mg²⁺ lost and the structural layers were dismantled. The micropore area significantly reduced due to the structural microhole collapsed, and the HCHO absorption capacity drastically declined. The sepiolite heated at ≥500 ℃ lost its HCHO adsorption ability for the sepiolite phase was decomposed with the crystalliferous water completely lost and the structural microhole collapsed also. The research affirmed continuously removing HCHO in the air with sepiolite by heating at reasonable temperature that could not only eliminate the absorbed HCHO and regenerate the adsorption capacity.