The invention discloses a children qi-restoring decoction, and a formula and a preparation method thereof. The children qi-restoring decoction provided by the invention comprises the following medicinal material decoctions: pericarpium citri reticulatae viride, pericarpium citri reticulatae, betel nut, fructus quisqualis, medicated leaven, semen alpiniae katsumadai, simmered ginger and dried rehmannia glutinosa. The children qi-restoring decoction is prepared from 3-7 g of pericarpium citri reticulatae viride, 3-7 g of pericarpium citri reticulatae, 3-7 g of betel nut, 3-7 g of fructus quisqualis, 3-7 g of medicated leaven, 3-7 g of semen alpiniae katsumadai, 3-7 g of simmered ginger, 3-7 g of dried rehmannia glutinosa and the like. After the children qi-restoring decoction is taken, the children qi-restoring decoction plays roles in invigorating spleen and nourishing stomach, promoting digestion, killing insects and removing accumulation, so as to improve and treat thalassemia.