Abstract: Flexible Ti₃C₂T_x MXene/polyvinyl alcohol (PVA) composites with high dielectric constant were fabricated by using the solution casting method with two-dimensional transition metal carbide Ti₃C₂T_x MXene as the filler and non-ferroelectric and biodegradable polyvinyl alcohol (PVA) as the matrix. The effect of Ti₃C₂T_x MXene loading on the dielectric properties of the composites were investigated. The variation of dielectric properties of the Ti₃C₂T_x MXene/PVA composites conforms to the percolation theory. With the increase of Ti₃C₂T_x MXene loading, the dielectric constant of Ti₃C₂T_x MXene/PVA composites first increases and then decreases. The composites show a dielectric constant up to 577.3 at 20 Hz frequency with Ti₃C₂T_x MXene loading of 20wt%, a 5 398% increase compared with that of the neat PVA matrix. When the Ti₃C₂T_x MXene loading exceeds 20wt%, the dielectric constant of the Ti₃C₂T_x MXene/PVA composites decreases sharply and the dielectric loss increases rapidly, showing obvious percolation behavior.