The invention provides a microband microwave absorbing device and a method based on a phase-adjustable supersurface, comprising at least one unit structure. The unit structure comprises a metal structure, a dielectric substrate, a first via, a second via, a ground substrate, a varactor diode, a first via, a second via penetrating the dielectric substrate and the ground substrate, and one end of the first via hole is connected to the metal structure, and the varactor diode is connected between symmetrical metal structures of the metal structure. The control unit adjusts the phase response distribution of the cell structure by providing a reverse bias voltage to the cell structure and adjusting the varactor diode. By applying the bias voltage to the sub-wavelength cell to change the electromagnetic state, the independent phase of the super-surface cell structure can be adjusted, and then the reflected phase of the incident field in the super-surface cell structure can be arbitrarily changed, which has the characteristics of simple design, easy processing, flexible application and so on.