The invention discloses a solar dehumidification system for an underground space. The solar dehumidification system comprises a solar heat utilization part, a concentrated solution regeneration part and an underground space dehumidification part. The solar heat utilization part comprises a dilute solution storage tank, a three-way reversing valve, a solar heat collector, a temperature controller and an air source heat pump hot water unit, wherein the solar heat collector is introduced into an open type pulsating heat pipe, so that the temperature of a dilute solution is increased, and water evaporation in the solution regeneration part is promoted; the concentrated solution regeneration part comprises a dehumidification solution regenerator, a first solution pump, a heat regenerator, an air cooler and a concentrated solution storage tank, and the solution concentration is increased by using a flash evaporation technology of liquid dehumidification; and the underground space dehumidification part comprises a second solution pump, a fan, a first temperature detector, a humidity detector, a film type dehumidifier, a third solution pump, a humidity controller and a second temperature detector, and the air humidity is reduced by using a film dehumidification technology. Therefore, the system not only realizes efficient pollution-free dehumidification of the underground space, but also can solve the problems that the regeneration concentration is low and the dehumidified air is easy to carry a dehumidification solution in a liquid solution dehumidification technology.