The invention provides a medicine for treating malignant pleural effusion with syndrome of phlegm-dampness due to spleen deficiency. The medicine consists of the following medicinal raw materials: rheum officinale, semen lepidii, radix curcumae, cassia twig, bigflower cape jasmine fruit, pseudobulbus cremastrae seu pleiones, selfheal, codonopsis pilosula, dried ginger, schisandra chinensis, hemarthria sibirica, oriental dodartia herb, platycodon grandiflorum, radix angelicae pubescentis, herba ephedra, radix liriopes, fructus arctii, bighead atractylodes rhizome, radix scrophulariae, rhizoma acori graminei and liquorice root. The medicine, in combination with pleural infusion chemotherapy, provides an effective means for treating malignant pleural effusion, so as to relieve the reoccurrence speed of lung cancer with pleural effusion and to enhance a curative effect; in addition, in combination with traditional Chinese medicines, the medicine can relieve toxic and side effects caused by the chemotherapy and consolidate the curative effect; and meanwhile, the medicine can improve life quality and relieve clinical symptoms of a patient, and can give consideration to both the whole and the part of the patient, so as to achieve purposes of strengthening body resistance and eliminating evil.