The invention discloses a testing apparatus for simulating action of concrete meeting water after a high-temperature fire hazard and a testing method thereof to provide technical support for related fire-fighting simulation tests, belonging to the technical field of testing of concrete materials. The testing apparatus is provided with a workbench, a cooling device, etc. The apparatus provided by the invention is low in price and simple in structure; and the testing method is simple to operate, safe, reliable, stable in performance and good in applicability. The apparatus used in the testing method can accurately adjust a contact area between a test piece exposed to fire and cooling water, and conducts research on influence of natural cooling, water cooling, different cooling time and different cooling area on damage to concrete having undergone high-temperature fire hazards. Concrete test pieces exposed to high-temperature fires are detected in each cooling pattern, and research is conducted on the interior and exterior damage situations of concrete, the strength changing rule of concrete, the deformation changing rule of concrete, the endurance changing rule of concrete and the like on the basis of detection results.