The invention discloses pyridine amino pyrimidine derivative salt, a preparation method thereof and an application, and provides mesylate of a compound as shown in a formula (I), a preparation method of the mesylate, a medicine composition with the salt and an application of the salt to treatment of EGFR (epidermal growth factor receptor) activated or drug-resistant mutant mediated diseases, particularly cancers of mammals, particularly human bodies. The mesylate of the compound as shown in the formula (I) is high in bioavailability in animal bodies, can more effectively inhibit growth of animal transplantation tumors and displays good safety.