The present invention belongs to the field of medical chemistry, and relates to a class of heterocyclic compounds acting as ASK inhibitors and the use thereof. Specifically, provided are compounds as shown in formula A or isomers, pharmaceutically acceptable salts, solvates, crystals or prodrugs thereof, methods for preparing same, pharmaceutical compositions containing these compounds and the use of these compounds or compositions in treating and/or preventing diseases associated with apoptosis signal-regulating kinase 1. The compounds of the present invention have an excellent apoptosis signal-regulating kinase 1 inhibitory activity, and show a great deal of promise in becoming therapeutic agents for diseases associated with apoptosis signal-regulating kinase 1.