In this work, gold nanoparticles (AuNPs) decorated Ti₃C₂T_x nanosheets (MXene/AuNPs composite) are fabricated through a self-reduction reaction of Ti₃C₂T_x nanosheets with HAuCl₄ aqueous solution. The obtained composite is characterized as AuNPs with the diameter of about 23 nm uniformly dispersing on Ti₃C₂T_x nanosheets without aggregation. The composite (MXene decorated on 4.8 wt% AuNPs) is further employed to construct supercapacitor for the first time with a higher specific capacitance of 278 F·g^-1 at 5 mV·s^-1 than that of pure Ti₃C₂T_x and 95% of cyclic stability after 10,000 cycles. Furthermore, MXene/AuNPs composite symmetric supercapacitor with filter paper as separator and H₂SO₄ as electrolyte, is assembled. The supercapacitor exhibits a high volumetric energy density of 8.82 Wh·L^-1 at a power density of 264.6 W·L^-1 and ultrafast-charging/ discharging performance. It exhibits as a promising candidate applied in integrated and flexible supercapacitors.