The invention discloses a method for preparing low-As-content tree moss absolute by molecular distillation. The method successively comprises the following steps: 1) carrying out the molecular distillation on commercially available tree moss absolute under certain conditions to obtain light-component and heavy-component substances at low temperature; 2) carrying out ethanol redissolution and freezing-separation on the heavy-component substances, or performing water washing after dissolving by ethyl acetate to reduce the As content in the heavy-component substances, and improving the liquidity of heavy components to obtain processed heavy-component substances; 3) carrying out the molecular distillation again on the processed heavy-component substances under certain conditions to obtain the light-component substances at high temperature, 4) mixing the light-component substances under the low temperature and the light-component substances under the high temperature, thus obtaining a product of the low-As-content tree moss absolute. The tree moss absolute obtained by using the method disclosed by the invention is a mixture of light components obtained by carrying out the molecular distillation for two times, the light-component substances are mainly used as aroma active components of tree moss, less in impurities, better in aroma quality and lower in As content, in addition, the treatment process is suitable for production.