The invention discloses novel application of 1,4,5,6-tetralin-2-methyl-4-pyrimidinyl carboxy in the medical field, and particularly relates to application in preparing a medicament for treating digestive tract diseases caused by chemotherapy medicaments. The inventor is surprised to find in researches that: the 1,4,5,6-tetralin-2-methyl-4-pyrimidinyl carboxy and derivatives thereof have unexpected treatment effect on gastritis, gastric ulcer and duodenal ulcer caused by chemotherapy medicaments, so that the 1,4,5,6-tetralin-2-methyl-4-pyrimidinyl carboxy and derivatives thereof can be used inpreparing medicaments for treating gastritis, gastric ulcer and duodenal ulcer caused by chemotherapy medicaments. The invention also provides a medicament for treating digestive tract diseases, which consists of ectoine or derivatives thereof and medically acceptable pharmaceutic adjuvant. Experiments prove that: the ectoine and derivatives thereof have good treatment effect on the gastritis, the gastric ulcer, the duodenal ulcer and other digestive tract diseases, and is superior to ranitidine, Sanjiu Weitai, domperidone and other medicaments.