【Objective】To investigate the role and the potential target of miR-199a-3p in mouse cardiac hypertrophy.【Methods】Neonatal mouse ventricular cardiomyocytes（NMVC）were isolated from the hearts of 0- 3- day- old newborn C57BL/6 mice. MiR-199a-3p mimic and retinoblastoma transcriptional corepressor 1（Rb-1）siRNA were transfected in? to NMVC to elevate the level of miR-199a-3p and inhibit Rb-1 expression，respectively. NMVC were stained with FITC- phalloidin solution to determine the size of NMVC. Dual luciferase reporter assay was performed to identify the interaction between miR- 199a- 3p and the 3’UTR of Rb- 1. mRNA and protein expression of cardiac hypertrophy associated genes were determined by RT-qPCR and Western blotting assay，respectively.【Results】（1）Over-expression of miR-199a-3pcould significantly enhance the expression of cardiac hypertrophy-related genes in NMVC ；（2）Dual-luciferase reporter assay results verified that miR- 199a-3p can interact with the 3’UTR of Rb-1. MiR-199a-3p could suppress Rb-1 ex? pression at the post-transcriptional level；（3）Functionally，miR-199a-3p mimic，consistent with Rb-1 siRNA，could increase cell size and the expression of Nppa，Acta1 and Myh7 in NMVC，and promote the nuclear translocation of E2f2 in NMVC.【Conclusions】MiR-199a-3p promotes the entry of E2f2 into the nucleus through inhibiting the expression of Rb-1，contributing to cardiomyocyte hypertrophy.