Objective To investigate the application value of ultrasound and magnetic resonance imaging (MRI) in the diagnosis of left ventricular aneurysm (LVA) after myocardial infarction (CI). Methods The clinical data of 54 patients with suspected LVA after CI between January 2016 and December 2017 were retrospectively analyzed. The results of pathological examination were used as controls, and the patients were given ultrasonic cardiogram, MRI and coronary angiography. The application value of ultrasound and MRI in the diagnosis of LVA after CI was compared, and the sensitivity, specificity, accuracy, negative predictive value and positive predictive value were calculated. Results The detection rates of LVA by ultrasonic cardiogram and MRI were 100%, and the accuracy rates in diagnosis of LVA distribution were also 100%, and there was no significant difference between the two groups (P>0.05). The detection rate of paradoxical movement area by MRI was significantly higher than that by ultrasonic cardiogram (P<0.05). The accuracy rate in diagnosis of LVA after CI by MRI was higher than that by ultrasound (P<0.05). Conclusion Both ultrasound and MRI have clinical application value in the diagnosis of LVA after CI. And MRI is more conducive to the differential diagnosis and judgment of LVA condition.