Abstract: Provided are an exhaust gas vessel denitration system and a method of determining nozzle clogging in the same, and more particularly, an exhaust gas vessel denitration system including an exhaust pipe for discharging exhaust gas including nitrogen oxide generated from an engine of a vessel, a reducing agent inlet configured as an integrated dosing unit (IDU) for injecting a reducing agent into the exhaust pipe, and a reactor for inducing a reduction reaction of exhaust gas mixed with the reducing agent and decomposing nitrogen oxide in the exhaust gas to nitrogen and water vapor to reduce the nitrogen oxide, and a method of determining clogging of urea spray at an injector nozzle of the system.