The invention discloses a condensing dehumidification and solution dehumidification combined fresh air treatment device and method. According to the device and method, an air circulation system, two refrigerant circulations and two solution circulations are included; after fresh air and return air are subjected to full heat exchange, condensing dehumidification is conducted through a surface air cooler firstly, and dehumidification and thermoregulation are conducted through a solution dehumidifier till the ideal air supply state is reached; the return air and the other part of fresh air are used for solution regeneration and condensation heat treatment, and dynamic matching of the heat among key components in the device and solution parameters along with fresh air treatment load changes can be achieved by adjusting the fresh air flow of an exhaust duct; selective permeable membrane cores are adopted for both the solution dehumidifier and a regenerator, and supplied air and exhausted air with liquid can be avoided; and the energy-saving effect of the device is remarkable, and the problems that by means of a conventional solution dehumidification air treatment device, the operating parameters are difficult to match, liquid is carried, and the air supply parameter control is not precise are solved.