Stem rot， a devastating soil-borne disease caused by the pathogenic fungus Sclerotium rolfsii Sacc.， is a major constraint to peanut production in China and other countries worldwide. In this study， five widely cultivated peanut accessions from northeastern China—Fuhua 18， Huayu 22， Huayu 23， Jinhua 15， and Qinghua 6—were inoculated with three S. rolfsii isolates （SrSD1， SrHB1， and SrLN1， originating from Shandong， Hebei， and Liaoning provinces， respectively） to investigate disease progression. The disease index increased steadily from day 3 post-inoculation， with most plants succumbing by day 12. To identify new germplasm resources resistant to stem rot， 703 peanut accessions were examined for resistance at the seedling stage. Significant differences in virulence were observed among the three isolates， with SrLN1 （from Liaoning） being the most aggressive. Resistance levels also varied among germplasm from different regions， with accessions from Guangdong and Zhejiang provinces demonstrating greater resistance than those from other areas. Three accessions—SNHD132， SNHD072， and Baihuashengfen—exhibited moderate resistance to all three isolates in seedling assays. Subsequent detached organ inoculation and field trials confirmed that these moderately resistant accessions exhibited significantly reduced lesion expansion compared to high susceptible controls （SNPN192， Huayu 26， and Jinhua 15）. Field evaluations further revealed that these accessions had significantly lower plant mortality， seed kernel infection rates， and yield losses than susceptible genotypes. Through a combination of seedling-stage， detached organ， and field evaluations， this study identified promising resistant germplasm， offering valuable resources and a theoretical foundation for breeding stem rot-resistant peanut varieties and investigating resistance mechanisms.