In the framework of the QCD factorization approach, we study the localized $CP$ violations of the $B^-\rightarrow K^- π^+π^-$ decay with and without $a_0^0(980)-f_0(980)$ mixing mechanism, respectively, and find that the localized $CP$ violation can be enhanced by this mixing effect when the mass of the $π^+π^-$ pair is in the vicinity of the $f_0(980)$ resonance. The corresponding theoretical prediction results are $\mathcal{A}_{CP}(B^-\rightarrow K f_0 \rightarrow K^-π^+π^-)=[0.24, 0.36]$ and $\mathcal{A}_{CP}(B^-\rightarrow K^- f_0(a_0) \rightarrow K^-π^+π^-)=[0.33, 0.52]$, respectively. Meanwhile, we also calculate the branching fraction of the $B^-\rightarrow K^-f_0(980)\rightarrow K^-π^+π^-$ decay, which is consistent with the experimental results. We suggest that $a_0^0(980)-f_0(980)$ mixing mechanism should be considered when studying the $CP$ violation of the $B$ or $D$ mesons decays theoretically and experimentally.

11 pages, 3 figures