The invention provides an adsorption testing method and an apparatus thereof. The adsorption testing method is characterized in that by measuring gas pressure before and after absorption in a reactorloaded with a sample, and a gas state equation is used to calculate molar weight of adsorption gas of the sample. The adsorption testing apparatus comprises pressure measuring equipment, vacuum generation equipment, a calculating module, and a gas supply unit for providing gas used for adsorption, a quantification pipe and a reactor which are connected in order according to an air-flow direction,the quantification pipe and the reactor have inner cavities with fixed volume, the sample is loaded in the inner cavity of the reactor, the pressure measuring equipment is used for measuring the gas pressure in the inner cavity of the reactor and the quantification pipe; the vacuum generation equipment is connected with the quantification pipe, the computer module is used for receiving the gas pressure measured by the pressure measuring equipment, and the gas pressure is set as total adsorption quantity delta n of the gas used for adsorption by the sample. The method and the apparatus can be used for efficiently and accurately detecting the adsorption quantity of the gas by the sample under condition that physical properties of the experiment sample cannot be changed.