In the environmental control and life support system (ECLSS) of the extravehicular spacesuit, the removal of the moisture from the medium gas can be achieved by the dehumidifier which may effectively improve the sensitivity of the CO₂ pressure sensor. In order to adapt the usage mode and egress time of the extravehicular spacesuit, and to extend the usage times of the dehumidifier, a method of the residual oxygen purging is proposed, by which the color-changing silica gel is regenerated after dehumidification. This method aims to study the dehumidification performance, the regenerative performance and the influence of the usage mode on the dehumidification performance. Firstly, the physical properties and the dehumidification performances of the desiccants such as the calcium chloride (CaCl₂), color-changing silica gel, and fine porous silica gel are compared and analyzed using the dehumidifier. Secondly, the method of the residual oxygen purging is tested, by which the color-changing silica gel is regenerated after dehumidification. Finally, the influence of the usage mode on the dehumidification performance of the dehumidifier was experimentally investigated and compared. The experimental results indicate that the dehumidification performance of CaCl₂ is better than that of color-changing silica gel, but the CaCl₂ particle tends to collapse and short circuit after hygroscopic. Under the same condition, the continuous dehumidification time of the color-changing silica gel is 32 h, while the time of the fine porous silica gel is 23 h. After a pause of dehumidification, the dehumidification performance of the dehumidifier change. The outlet humidity of the intermittent usage mode increases with the increase in dehumidification time, which is higher than that of the normal usage mode. Furthermore, the physical characteristics of color-changing silica gel are stable, and it has a longer dehumidifying time under the conditions of the dehumidification requirements, making it more suitable for the dehumidifier in this system. Additionally, the color-changing silica gel can be recycled and has the ability to multiple dehumidify after being purged with pure oxygen. However, the discontinuous mode can lead to the redistribution of the moisture within the silica gel, reducing the overall moisture absorption capacity of the dehumidifier. This research provides fundamental data and theoretical guidance for the desiccation selection of the dehumidifier and optimization of regeneration characteristics of the extravehicular spacesuit in environmental control and life support system.