Ti3C2Tx is a promising new two-dimensional layered material for supercapacitors with good electrical conductivity and chemical stability. However, Ti3C2Tx has problems such as collapse of the layered structure and low pseudocapacitance. In this paper, we propose Bi2O3–Ti3C2Tx nanocomposites prepared by a solvothermal method, study the impact of Bi2O3 loading on the phase state and microstructure, and evaluate the electrochemical performance of Bi2O3–Ti3C2Tx. Studies have shown that spherical Bi2O3 particles were uniformly dispersed in the interlayer and surface of Ti3C2Tx, which enlarged the interlayer spacing of the Ti3C2Tx and increased the pseudocapacitance. When the mass percentage of Bi2O3 and Ti3C2Tx was 30% (TB30), the specific capacity of TB30 was as high as 183 F g−1 at a current density of 0.2 A g−1, which was about 2.8 times that of Ti3C2Tx (TB0). Moreover, a typical asymmetric supercapacitor device assembled with TB0 as the positive electrode and TB30 as the negative electrode exhibited a high energy density of 3.92 W h kg−1 and a maximum power density of 36 000 W kg−1 and maintained 77.4% of the initial capacitance after 5000 cycles at a current density of 2 A g−1. Therefore, the Bi2O3–Ti3C2Tx as the negative electrode of supercapacitor has broad application prospects in the field of energy storage.