In this paper, a reconfigurable frequency selective absorber based on liquid metal (LM) has been proposed. The unit cell consists of two layers, and two polymethylmethacrylate (PMMA) substrates with different channels are located on the upper and bottom layers respectively. By changing the filling of LM in the channels, this design can switch between absorption, transmission, and reflection around 5.1 GHz, while maintaining the absorption performance on both sides of the reconfigurable frequency band.