Objective To investigate the value of quantitative 3.0T cardiac magnetic resonance（CMR） techniques for diagnosing the efficacy of acute viral myocarditis（AVM）and assessing short⁃term prognosis. Meth⁃ ods 115 patients with suspected AVM from January 2019 to August 2021 in our hospital were selected and divid⁃ ed into AVM and non ⁃AVM groups with reference to clinical diagnosis，to evaluate the diagnostic value of 3.0T CMR quantitative parameters［T2 ratio，early intensification imaging（EGE）ratio，delayed intensification imaging （LGE）volume，and LGE as a percentage of left ventricular mass］for AVM，and patients with AVM were Patients with AVM were followed up for 3 months，prognosis was counted，3.0T CMR quantitative parameters were com⁃ pared in patients with different prognosis，and the relationship between each parameter and prognosis was analyzed. Results Clinical diagnosis showed that 81 patients with confirmed AVM and 34 patients with non⁃AVM；T2 ra⁃ tio，EGE ratio，LGE volume，and LGE as a percentage of LV mass were higher in the AVM group than in the non⁃ AVM group（P < 0.05）；the AUC of T2 ratio，EGE ratio，LGE volume，and LGE as a percentage of LV mass for the combined diagnosis of AVM was 0.908（95% CI：0.840 to 0.954）was significantly greater than the single diag⁃ nosis of each parameter（all P < 0.05）. Using the most truncated value obtained from the ROC curve as the bound⁃ ary，divided into positive and negative，the risk of AVM occurrence was 8.815 times，2.938 times，2.183 times， and 4.337 times higher in patients with positive T2 ratio，EGE ratio，LGE volume，and LGE as a percentage of LV mass than in patients with negative；at 3⁃month follow ⁃up，the AVM group had a good prognosis in 67 cases，a poor prognosis in 14 cases，and a poor prognosis in T2 ratio，EGE ratio，LGE volume，and percentage of LGE to LV mass were higher than those of patients with good prognosis（P < 0.05）；T2 ratio，EGE ratio，LGE volume， and percentage of LGE to LV mass were negatively correlated with short⁃term prognosis of AVM（P < 0.05）.Conclusion The 3.0T CMR quantitative technique can be used as a reliable imaging modality for clinical diagno⁃ sis of AVM and also for short⁃term prognostic assessment，which can provide effective objective information for clin⁃ ical diagnosis and treatment.