The extensive existing of microplastics (MPs) in the ecosystem have increased considerable attention concerning their potential adverse effects, the toxicities and the underlying mechanism of MPs are still scarce. To explore the effect of MPs on cardiac tissue in Wistar rats and unravel the mechanism of pyroptosis and oxidative stress in the process of cardiomyocytes injury, 32 male Wister rats were divided into control group and three model groups, which were exposed to 0.5 mm PS MPs at 0.5, 5 and 50 mg/L for 90 days. Results revealed that MPs could damage cardiac structure and function with impaired mitochondria integrity, as well as increased levels of creatine kinase‐MB and cardiac troponinI (cTnI). Moreover, MPs administration triggered oxidative stress as indicated by increased levels of malondialdehyde and decreased activity of superoxide dismutase, glutathione peroxidase and catalase. Treatment with MPs resulted in apoptosis and pyroptosis as evidenced by increasing expressions of interleukin (IL)‐1β, IL‐18. Additionally, MPs were shown to induce the NOD‐like receptor protein 3 inflammasomes activation in cardiac tissue, enabling activation of Caspase‐1‐dependent signaling pathway induced by inflammatory stimuli resulting from oxidative stress. In summary, these results illustrated that pyroptosis played a vital role in polystyrene MPs‐induced cardiotoxicity, which might be helpful to understand the mechanism of cardiac dysfunction and induced by MPs.