This invention relates to Ligulatrovine A separated from Ligularia actroviolacea that can prevent and treat diseases related to Staphylococcus aureus and beta hemolytic streptococcus, its pharmaceutical salts and drug composition. Ligulatrovine A has significant inhibitive effect on Gram-positive bacteria, and can prevent and treat diseases such as boil, pustule, pneumonia, osteomyelitis, acute myocarditis, endocarditis, meningitis, mastitis, cystitis, pelvic inflammation, urinary inflammation, prostatitis, bacteremia, or abscess in muscle, skin, urogential region or central nervous system caused by Gram-positive bacteria infection.