The invention provides a substituted heteroaryl compound, a composition thereof and application of the substituted heteroaryl compound and the composition. The compound is a compound shown in a formula (I) or a stereisomer, or a tautomer, or nitric oxide, or solvate, or a metabolite, or a pharmaceutically acceptable salt or a prodrug of the compound shown in the formula (I). The invention further provides the drug composition containing the compound, and the compound and the drug composition can adjust activity of JAK kinase and are used for preventing, handling, treating, and relieving diseases or disorder mediated by the JAK kinase.