To reveal the morphological pattern of Isaria cicadae.We observed 17 morphological characters and measured 75 strains of 15 populations in I. cicadae. Statistical analysis system (SAS) 8.1 was used to analyze the morphological data, the morphological pattern was analyzed in 15 populations of I. cicadae, using the descriptive statistical analysis, nested analysis and Q cluster analysis.Two types of asexual conidium (large and small conidium) were observed in I. cicadae. The gourd-shaped and bottle-shaped conidiogenous cells were observed in I. cicadae. Many chlamydospores of I. cicadae were easy to form in PDA medium. Many fusion hyphae were generated between hyphae, and some fusion hyphae between hypha and chlamydospore, the fusion hyphae between conidiogenous cells were also observed. The CV of 17 morphological characters was from 13.07 to 104.09% in I. cicadae, indicating an ample morphological diversity at the species level. The nested variation analysis of the 17 morphological characters indicated that about 11.29% of the variability was attributable to the differentiation among populations, the rest 15.27% of the variability was derived from individual strains, and the remaining 73.44% was resided in the observations in the same strain.The phenotypic variation within strain was the main morphological variation of I. cicadae. The morphological characters had no significant relationship with geographical origin in I. cicadae.