Objective To investigate the effect of the amyloid beta precursor protein binding protein B1 (Apbb1) gene on H9c2 cardiomyocyte proliferation and its potential mechanism. Methods H9c2 cardiomyocytes were treated with small interfering RNA and pcDNA3. 1⁺ plasmid for knockdown and overexpression of the Apbb1 gene, and cell proliferation was detected by CCK8, qPCR and immunofluorescence assay, to evaluate the effect of this gene on cardiomyocyte proliferation. Next, the proteins interacting with the Apbb1 protein were analyzed using the online database String to explore how Apbb1 might function. In the experiment, four groups were established: knockdown control group, Apbb1- knockdown group, overexpression control group and Apbb1-overexpression group. Results Compared with that in the knockdown control group, expression of the Apbb1 gene in the Apbb1-knockdown group decreased by 52% (P<0.05, n= 3) and cell proliferation decreased by 44% at 48 h (P<0.01, n= 3), but cell proliferation increased by 86% at 72 h (P< 0.0001, n= 3). The expression levels of Ccnb1 and Ccna2 mRNA were increased by 80% (P<0.001, n= 3) and 76% (P<0.001, n= 3), respectively. Immunofluorescence assay showed that PH3- and Aurora B-positive cells increased by 4. 33% (P< 0.01, n= 3) and 4. 67% (P< 0.05, n= 3). Compared with that in the overexpression control group, the expression of the Apbb1 gene was upregulated 119-fold in the Apbb1-overexpression group (P<0.0001, n= 3), and cell proliferation decreased by 1. 23 times at 48 h (P< 0.0001, n= 3) and 1. 04 times at 72 h ( P< 0.0001, n= 3). The expression levels of Ki67, a marker of cell proliferation, and Ccnb1 and Ccna2 mRNA encoded by cell cycle-related genes were decreased by 25% ( P< 0.01, n= 3), 72% ( P< 0.001, n= 3), and 38% ( P< 0.001, n= 3), respectively. Meanwhile, PH3- and Aurora B-positive cells decreased by 3. 7% (P< 0.01, n= 3) and 4. 36% (P< 0.05, n= 3), respectively. The result of protein interaction network analysis showed that KAT5, APP and APLP2 were the proteins that most significantly interacted with Apbb1. Conclusions Knockdown of the Apbb1 gene promotes the proliferation of H9c2 cardiomyocytes, while its overexpression inhibits their proliferation. Apbb1 may affect the proliferation of cardiomyocytes by influencing the G2 / M phase of the cell cycle and KAT5 may interact with Apbb1 protein to affect cardiomyocyte proliferation .