The invention discloses a method for improving the pig cloning efficiency on the basis of inhibition of H3K9me3 methylation. According to the method, H3K9me3 methylation is inhibited by inhibiting expression of Suv39H1 and Suv39H2 genes in nuclear donor cells during nuclear transplantation of a cloned embryo of a pig and overexpression of KDM4A mRNA during nuclear transplantation of a reconstructed embryo, and the pig cloning efficiency is further improved. Specifically, according to the method for improving the pig cloning efficiency, effective siRNA resisting Suv39H1 and Suv39H2 genes is co-transfected in the nuclear donor cells before nuclear transplantation, overexpression of the Suv39H1 and Suv39H2 genes in the nuclear donor cells is inhibited, accordingly, the high methylation level of H3K9me3 in the nuclear donor cells is inhibited, the processed nuclear donor cells are subjected to nuclear transplantation, cytoplasm microinjection of KDM4A mRNA is performed after the reconstructed embryo obtained after nuclear transplantation is activated, methylation of histone H3K9me3 in the reconstructed embryo is further inhibited, and the cloning efficiency of the pig is finally improved.