NaNbO₃ (NN) crystals with preferential growth of the [101] crystal axis were prepared by the molten salt method. Based on use of the prepared [101]-oriented NN powder as the raw material, BT/NN composite ceramics were prepared by the conventional solid-state reaction method. The effects of the amount of NN and sintering temperature on the microstructure and dielectric properties of the BT/NN composite ceramics were systematically studied. The optimal component ratio for the preparation of composite ceramics was explored by adjusting the contents of BT and NN. When BT: NN is 5 : 5, the dielectric constant of the BT/NN composite is 1112, which is higher than the dielectric constant of the single-component BT of 658 and NN of 550. Simultaneously, the phase transition temperature of composite ceramics is approximately 416 °C, which is significantly higher than the phase transition temperature of pure NN of 338 °C, further improving the phase stability of the NN structure. The preparation of BT/NN composite ceramics provides important guidance for the design of the ferroelectric-antiferroelectric composites and improvement of lead-free piezoelectric ceramics.