The invention relates to modified silicon dioxide nanoparticles, and a preparation method and applications thereof, and belongs to the technical field of nano material preparation. The preparation method comprises following steps: firstly, nano silicon dioxide particles and 3-chloropropyltriethoxysilane are added into an absolute ethyl alcohol solution, reflux reaction is carried out, and an obtained solid substance 1 is marked as COTS-SNPs; the COTS-SNPs is added into a 4,4-bipyridine solution, vinyl chloride, methylbenzene, and CuCl are added successively, reflux reaction is carried out, and an obtained solid substance 2 is marked as VC-SNPs; the obtained VC-SNPs is added into an absolute ethyl alcohol solution, triethylamine and 1-methylimidazole are added, reflux reaction is carried out, and an obtained solid substance 3, which is the modified silicon dioxide nanoparticles, is collected, and is marked as MDZ-SNPs. The obtained modified silicon dioxide nanoparticles can be taken as an adsorbent to absorbing palladium ions in solution, are cheap, are convenient to synthesis, can be easily separated with aqueous solution, possesses high adsorptivity, and can be recycled.