Electromagnetic (EM) absorption plays a foremost important role in the area of energy harvesting, stealth technology, interference shielding and biological imaging etc. Perfect metamaterial/metasurface absorber, which obtains near-unity EM absorption through subwavelength artificial structure, usually suffers from narrow bandwidth. Here, for the first time, we demonstrate a curved water-based metasurface which functions as an active ultra-broadband absorbing material working across the entire Ku, K and Ka bands. Distinct from conventional metallic metamaterial/metasurface, the proposed water-based metasurface acquires broadband absorption property from the dielectric Mie resonance and periodic grating effect, which exhibits an experimental absorptivity of ∼99% and an absorption bandwidth (absorptivity higher than 90%) that covers 71.4% of the central frequency. Furthermore, near-unity absorption is maintained when the soft metasurface is bent into different curvatures, promoting its potential applications on non-planar circumstances.