The invention belongs to the field of dehumidifiers, and particularly relates to a variable-capacity dehumidifier. The variable-capacity dehumidifier comprises a base, an outer water tank is fixedly mounted at the top of the base, an inner water tank is movably mounted in the outer water tank, the top of the inner water tank extends out of the outer water tank, a mounting seat is fixedly mounted at the top of the inner water tank, a dehumidifier body is fixedly mounted at the top of the mounting seat, and a 3D projection device is installed at the top of the dehumidifier body. By means of reasonable structural design, the two water tanks are stacked together, when the water storage capacity is increased, the inner water tank automatically rises, the two water tanks store water at the sametime, the water storage capacity is increased under the condition that the occupied space of the dehumidifier is not changed, and meanwhile, the dehumidifier is further provided with 3D projection, different visual images such as deserts, oceans and forests can be presented in the form of images when environmental humidity changes are recognized, a user can know whether the indoor humidity environment is suitable or not as soon as possible, and the purposes of humanization and intellectualization are achieved.