An electromagnetic-driving variable liquid aperture is designed and fabricated. It consists of a driving cavity, an optical cavity and a storage chamber, a polydimethylsiloxane (PDMS) elastic film, an annular magnet and a driving coil. The driving cavity is filled with dyeing liquid, while the colorless transparent liquid fills the optical cavity and the storage chamber. When applying current, the annular magnet moves downward driven by the magnetic field, leading to deformation of the PDMS film. Being squeezed by the moving magnet with the deforming film, the dyeing liquid flows from the driving cavity into the optical cavity, which contributes to the decrease of the clear aperture diameter in the optical cavity. Our proposed aperture performs continuous variable ability up to 2.775 mm in diameter of clear aperture, when the current increases from 0 to 0.33 A, and its relative transmittance ranges from 98.539% to 22.776%.