The invention relates to pleuromutilin compounds and a preparation method thereof, particularly to sulfanilamide pleuromutilin derivatives and a preparation method thereof, which belongs to the field of chemically synthesized antibacterial drugs. Sulfanilamide drugs can be competitive with PABA (para-aminobenzoic acid) to act on dihydrofolate synthetase in bacteria, so that PABA is prevented to serve as a raw material to synthesize folic acid required by bacteria, the amount of tetrahydrofolic acid with metabolic activity is reduced, and the growth and the reproduction of bacteria are inhibited. A chemical structure on the site C14 on a pleuromutilin three-ring framework is modified, and a sulfanilamide structure is introduced to the site C14 to obtain a novel valnemulin derivative which can be applied to screening and developing of new antibiotics.