The invention discloses organic aerogel as well as a preparation method and application of the organic aerogel. The organic aerogel is mainly prepared by dissolving an organic monomer or low polymer containing multiple sulfydryl groups and an organic monomer or low polymer containing multiple vinyl groups into an alcohol, ketone, amide, sulfoxide, furan, nitrile or benzene organic solvent in the molar ratio of the sulfydryl groups to the vinyl groups being 1:(0.5-3). The organic aerogel is cross-linked through a C-S bond of a low internal rotation barrier to form a three-dimensional network structure; the aerogel is endowed with good flexibility, has good blocking property, a porous structure, high specific surface area, low heat conductivity and adjustable light transmission, and can be applied to different occasions. By adopting efficient thiol-ene click reaction, the preparation process is simple, efficient, short in cycle and free of subsequent modification step; the prepared organic aerogel can be applied to the fields of building energy conservation, petrochemical engineering or sewage treatment.