An embodiment of the invention provides a system and a method for determining influence of to-be-measured gas on stratum rock. The system comprises a rock core clamp holder, a pressure tank, a to-be-measured gas tank, a brine tank, a temperature control box, a gas-liquid separator, a gas collecting bottle and a liquid collecting bottle. The rock core clamp holder comprises a clamping barrel and a sleeve, a first opening and a second opening are formed in two longitudinal ends of the clamping barrel, and a third opening and a fourth opening are symmetrically formed in the wall of the clamping barrel; a first end cover and a second end cover are arranged at two longitudinal ends of the sleeve, a first gas hole and a second gas hole are formed in the first end cover and the second end cover, and a third gas hole and a fourth gas hole are formed in the wall of the sleeve and correspond to the third opening and the fourth opening. The system and the method have the advantages that the influence of the gas on the stratum rock can be determined by the aid of the rock core clamping holder with the structure, and accordingly the technical problems of large errors of determination results, complicated operation and long time consumption of existing methods can be solved.