In this study, in situ nano-ZrB_2/2024 Al composites fabricated from 2024Al–K_2ZrF_6–KBF_4 system were processed by friction stir processing(FSP) to achieve superplasticity of the composites. And the effects of particle contents(1 wt%, 3 wt%, 5 wt%), matrix grain size(micron or submicron), strain rates(5×10~(-3)s~(-1), 1×10~(-2)s~(-1), 2×10~(-2)s~(-1) and deformation temperatures(400 K, 480 K, 600 K, 700 K, 750 K) on the superplasticity of the composites were investigated. After the friction stir processing, the coarse grains of the cast composites with matrix grain size of about 80–100 μm and nano-Zr B2 reinforcement size of 30–100 nm were crushed into small grains about 1 μm in size, and the uniformity of the nano-Zr B_2 reinforcements was also improved. And under the same superplastic tensile testing condition at the temperature of 750 K and strain rate of 5×10~(-3)s~(-1), the FSP nano 3 wt%Zr B_2/2024 Al composite exhibited an superplastic elongation of 292.5%, while the elongation of the corresponding cast composite was only less than 100%. Meanwhile, the m values of the FSP composites were always higher than the cast composites, especially the FSP composites with 3 wt% particles has the m value of 0.5321 i.e., the FSP composites should had better superplastic properties than cast ones. Furthermore, the FSP composites had higher apparent deformation activation energy(Q) than that of the lattice diffusion of pure aluminium, indicating that the deformation mechanisms of the FSP composites should be grain boundary sliding mechanisms. In this study, in situ nano-ZrB 2/2024 Al composites fabricated from 2024Al-K_2ZrF_6-KBF_4 system were processed by friction stir processing (FSP) to achieve superplasticity of the composites. And the effects of particle contents (1 wt%, 3 wt %, 5 wt%), matrix grain size (micron or submicron), strain rates (5 × 10 -3 s -1, 1 × 10 -2 s -1, 2 × 10 -2 s -1 and deformation temperatures (400 K, 480 K, 600 K, 700 K, 750 K) after the friction stir processing of the composites were investigated. of the cast composites with matrix grain size of about 80-100 μm and nano-Zr B2 reinforcement size of 30-100 nm were crushed into small grains about 1 μm in size, and the uniformity of the nano-Zr B 2 reinforcements was also improved . And under the same superplastic tensile testing condition at the temperature of 750 K and strain rate of 5 × 10 -3 s -1, the FSP nano 3 wt% Zr B_2 / 2024 Al composite composite an anomaly of 292.5%, while the elongation of the corresponding cast composite was only less than 100%. The m values ​​of the FSP composites were always higher than the cast composites, especially the FSP composites with 3 wt% particles has the m value of 0.5321 ie, the FSP composites had had better superplastic properties than cast ones. The FSP composites had higher apparent deformation activation energy (Q) than that of the lattice diffusion of pure aluminum, indicating that the deformation mechanisms of the FSP composites should be grain boundary sliding mechanisms.