The invention discloses a determination device and method for a moisture adsorption speed of an adsorbent. The device comprises an adsorption system and a moist air generation system, a vacuumizing system, a pressure meter, a thermograph and a humidity sensor which are connected with the adsorption system, wherein a fixed flat disc is arranged in the adsorption system and is used for containing a tested adsorbent. The determination method comprises the following steps: firstly, taking a certain amount of the tested adsorbent and putting the tested adsorbent into the fixed flat disc; then starting the vacuumizing system and carrying out vacuumizing treatment on the adsorption system; then shutting down the vacuumizing system and starting the moist air generation system; inflating generated moist air with pre-set temperature into the adsorption system; after pressure in the adsorption system is changed to reach target pressure, shutting down the moist air generation system and starting to test: recording a humidity change tendency in the adsorption system through the humidity sensor; calculating a standard moisture adsorption speed of the adsorbent according to the humidity change tendency, the volume, pressure and temperature of the adsorption system and the mass of the adsorbent. The determination device and method disclosed by the invention have the advantages of simplicity in operation, accuracy in testing and rapid analysis.