Inclusion Criteria:  Aged ≥18 ECOG performance status of 0 to 1. Life expectancy of more than 12 weeks. At least one measurable lesion exists.(RECIST 1.1) Histologically or cytologic confirmed HER2 positive gastrointestinal tumors who failed prior therapies.  Required laboratory values including following parameters:  ANC: ≥ 1.5 x 10^9/L, Platelet count: ≥ 80 x 10^9/L, Hemoglobin: ≥ 90 g/L, Total bilirubin: ≤ 1.5 x upper limit of normal, ULN, ALT and AST: ≤ 1.5 x ULN, BUN and creatine clearance rate: ≥ 50 mL/min LVEF: ≥ 50% QTcF: < 470 ms  Signed informed consent.  Exclusion Criteria:  Subjects with third space fluid that can not be controled by drainage or other methods. Subjects that are unable to swallow tablets, or dysfunction of gastrointestinal absorption. Less than 4 weeks from the last radiotherapy, chemotherapy, target therapy Subjects with uncontrolled hypokalemia and hypomagnesemia before study entry. Subjects who can not interrupt the using of the drugs that may cause QT prolongation during study. Receiving any other antitumor therapy. Known history of hypersensitivity to pyrotinib or any of it components. Ongoing infection (determined by investigator). History of immunodeficiency, including HIV-positive, suffering from other acquired, congenital immunodeficiency disease, or history of organ transplantation. Subjects had any heart disease, including: (1) angina; (2) requiring medication or clinically significant arrhythmia; (3) myocardial infarction; (4) heart failure; (5) Any heart diseases judged by investigator as unsuitable to participate in the trial. Female patients who are pregnancy, lactation or women who are of childbearing potential tested positive in baseline pregnancy test. Known history of neurological or psychiatric disease, including epilepsy or dementia.