To identify Cenococcum geophilum Fr., estimate their genetic diversity and study the effects on their genetic variation, 27 Chinese C. geophilum isolates from 6 host plant species and 5 French C. geophilum isolates were analyzed using morphological and molecular methods. The universal primers ITS1/ITS4 were used in PCR-RFLP to amplify the rDNA internal transcribed spacer (ITS) of tested C. geophilum isolates. The amplified products were digested with EcoR Ⅰ, Hinf Ⅰ, and Mbo Ⅰ, and the digested fragments of PCR products showed that there were obvious differences. A random primer (5′-CGCACCGCAC-3′) was employed in RAPD to amplify the genomic DNA of C. geophilum, and 19 detectable and reliable DNA bands of 300-2 000 bp size were observed. According to the number, position, and strength of the DNA bands in agarose gel, the genetic distance and the genetic similarity among C. geophilum isolates were calculated using the PopGen Ver. 1.31 dendrogram analysis software. A phylogenetic tree was constructed based on the genetic distance by the Neighbor-Joining/UPGMA in PHYLIP. The results suggest the high level of genetic diversity among C. geophilum isolates from the same or different hosts. The effects of geographical factors or host plant species on C. geophilum genetic variation are not obvious. To identify Cenococcum geophilum Fr., estimate their genetic diversity and study the effects on their genetic variation, 27 Chinese C. geophilum isolates from 6 host plant species and 5 French C. geophilum isolates were analyzed using morphological and molecular methods. The universal primers ITS1 / ITS4 were used in PCR-RFLP to amplify the rDNA internal transcribed spacer (ITS) of tested C. geophilum isolates. The amplified products were digested with EcoR I, Hinf I, and Mbo I, and the digested fragments of PCR products showed that There were obvious differences. A random primer (5’-CGCACCGCAC-3 ’) was employed in RAPD to amplify the genomic DNA of C. geophilum, and 19 detectable and reliable DNA bands of 300-2 000 bp size were observed. According to the number, position, and strength of the DNA bands in agarose gel, the genetic distance and the genetic similarity among C. geophilum isolates were calculated using the PopGen Ver. 1.31 dendrogram analysis software. A phylogenetic tree was constructed based on the genetic distance by the Neighbor-Joining / UPGMA in PHYLIP. The results suggest the high level of genetic diversity among C. geophilum isolates from the same or different hosts. The effects of geographical factors or host plant species on C geophilum genetic variation are not obvious.