The invention discloses a system and method for rapidly forming a water-soluble core and belongs to the technical field of material forming. The system for rapidly forming the water-soluble core comprises a box body, a microdroplet spraying device, a mixing device, a spreading device, a movable heating device, a space heating device, a powder heating device, a liquid distribution bin, a controller, a work cavity, a lifting working platform and a temperature measurement probe. The method for rapidly forming the water-soluble core comprises the steps that firstly, a core CAD geometric solid model is established firstly, liquid dropping process of all dispersed layers is completed by the microdroplet spraying device according to the operation track, extracted by a computer, of a liquid dropping device, and then the water-soluble core is manufactured. The system and method are particularly suitable for rapidly forming and manufacturing the core with a water-soluble inorganic salt solution as an adhesion agent. By the adoption of the system and method, the water-soluble cores which are in any complicated shapes can be directly manufactured; due to the fact that a core mould does not need to be manufactured according to the method, manufacturing cost is reduced, and a product development period is shortened.