The invention discloses a medicine for treating lung cancer pleural effusion. The medicine is prepared from the following raw materials: kansui root, euphorbia pekinensis, lilac daphne flower bud, semen brassicae, semen lepidii, cortex mori radicis, pinellia ternate, Chinese-date, grifola, poria cocos, cassia twig, plantain herb, bighead atractylodes rhizome, oldenlandia diffusa, Chinese lobelia, semen coicis, trichosanthes peel, root of red-rooted salvia, roasted draba nemorosa, verbena, perillaseed, rhizoma pinellinae praeparata, tribulus terrestris, herba lycopi, bunge pricklyash seed, reddish orange, leech, allium macrostemon, almond, liquorice, root of straight ladybell, radix ophiopogonis, radix polygonati officinalis, radices trichosanthis, cortex lycii radicis, woodlouse, bombyx batryticatus, earthworm, cricket, mole cricket, glycoalkaloids, bufo gargarizans, salvia chinensis, radix sophorae flavescentis, rhizoma pleionis, burdock, subprostrate sophora root, tripterygium glycosides, turtle shell, elecampane, frankincense, myrrh, bighead atractylodes rhizome, corydalis tuber and radix paeoniae alba. The medicine has obvious effects of discharging water and removing stasis on a patient with lung cancer pleural effusion, simultaneously can be used for tonifying qi, relieving cough and reducing sputum, nourishing the blood, promoting blood circulation and relieving pain, and resolving hard lumps and eliminating mass, so that the living quality of the patient is improved, the life is prolonged, and the effective rate can reach 90%.