【Objective】 To evaluate the effects of miR-148a-3p on calreticulin (CRT) expression and mitochondrial function in cardiomyocytes incubated with high glucose. 【Methods】 miR-148a-3p minic and inhibitor were used to intervene the H9c2 cardiomyocytes of rats. The expression of CRT protein was detected. Then the cells were divided into control group, high-glucose group (HG), HG +miR-148a-3p minic group, HG + miR-148a-3p minic + TG (CRT agonist) group, HG + miR-148a-3p inhibitor group, and HG + miR-148a-3p inhibitor + CRT- (CRT-siRNA) group. The content of adenosine triphosphate (ATP) and the level of reactive oxygen species (ROS), the activity of mitochondrial respiratory chain complex enzyme and apoptotic rate were detected. 【Results】 miR-148a-3p minic significantly inhibited the expression of CRT protein in cardiomyocytes, while miR-148a inhibitor increased the expression of CRT. miR-148a-3p minic inhibited the decrease of ATP production, the increase of ROS production and cell apoptosis, and the inactivity of mitochondrial respiratory chain complex enzyme in cardiomyocytes induced by high glucose, while TG weakened the above effects of miR-148a-3p minic. miR-148a inhibitor aggravated the mitochondrial injury and apoptosis of cardiomyocytes induced by high glucose, but the effects of miR-148a-3p inhibitor were partially blocked by CRT-siRNA. 【Conclusion】 miR-148a-3p negatively regulates the expression of CRT in cardiomyocytes and protects the mitochondrial injury and apoptosis induced by high-glucose through inhibiting CRT.