In this study, humidity adsorption capacity (HAC) activated alumina and silica gel were investigated. Adsorption experiments were performed at temperatures of 303.15 K and 313.15 Kelvin and 5 different humidity. The humidity box was designed and built for testing. The results showed that the adsorption rate of silica gel in all humidities ranges is higher than that of activated alumina. In 30% humidity, the HAC of silica gel is 5% higher than that of activated alumina. In the humidity range of 30 to 85%, the HAC of silica gel is 14% higher than that of activated alumina. In humidity above 85%, the HAC of activated alumina is close to that of silica gel, while in a humidity content of 99%, the HAC of silica gel is only 4% higher than that of activated alumina. In addition, with increasing temperature, the HAC of silica gel remained constant in all humidities, but the HAC of activated alumina in a humidity of 99% increased by 2%. In this study, five adsorption isotherm models were used to model the data obtained in the laboratory. From the results of all models, concluded that Langmuir and Dubinin-Radushkovic models are suitable for silica gel and the Harkin-Jura model is suitable for activated alumina.