A TFA-catalyzed dearomative cyanidation of isoquinoline is described, which provides a series of 1-cyanoisoquinolines in high yields under solvent-free conditions. This protocol is operated under mild and environmentally friendly conditions, utilizing readily available and cost-effective starting materials. The reaction features broad functional group compatibility, 100 mmol scale synthesis ability and operational simplicity, making it a significant potential approach for the synthesis of various biologically interesting isoquinolines via α C-cyanation.