Reactive oxygen species are damaging to cardiomyocytes. H9c2 cardiomyocytes are commonly used to study the cellular mechanisms and signal transduction in cardiomyocytes, and to evaluate the cardioprotective effects of drugs following oxidative damage. The present study developed a robust, automated high throughput screening (HTS) assay to identify cardioprotective agents from a traditional Chinese medicine (TCM) library using a H2O2‑induced oxidative damage model in H9c2 cells. Using this HTS format, several hits were identified as cardioprotective by detecting changes to cell viability using the cell counting kit (CCK)‑8 assay. Two TCM extracts, KY‑0520 and KY‑0538, were further investigated. The results of the present study demonstrated that treatment of oxidatively damaged cells with KY‑0520 or KY‑0538 markedly increased the cell viability and superoxide dismutase activity, decreased lactate dehydrogenase activity and malondialdehyde levels, and inhibited early growth response‑1 (Egr‑1) protein expression. The present study also demonstrated that KY‑0520 or KY‑0538 treatment protected H9c2 cells from H2O2‑induced apoptosis by altering the Bcl-2/Bax protein expression ratio, and decreasing the levels of cleaved caspase‑3. In addition, KY‑0520 and KY‑0538 reduced the phosphorylation of ERK1/2 and p38‑MAPK proteins, and inhibited the translocation of Egr‑1 from the cytoplasm to nucleus in H2O2-treated H9c2 cells. These findings suggested that oxidatively damaged H9c2 cells can be used for the identification of cardioprotective agents that reduce oxidative stress by measuring cell viabilities using CCK‑8 in an HTS format. The underlying mechanism of the cardioprotective activities of KY‑0520 and KY‑0538 may be attributed to their antioxidative activity, regulation of Egr‑1 and apoptosis‑associated proteins, and the inhibition of ERK1/2, p38-MAPK and Egr-1 signaling pathways.