Rhizoctonia solani, Fusarium moniliforme, F.oxysporum, F. graminearum, Sclerotium rolfsii and Pytliium aphanidermatum were isolated from diseased plants in heavily infected sorghum fields. Among them, the number of isolates of the former three organisms was far greater than that of the latter.The result of pathogenic detection indicated that R. solani AG5 was the sole pathogen of sorghum seedling disease, while the other five organisms only caused subsidiary infection because of their non-pathogenic nature to cotton seedlings. The best period for isolation from cotton seedlings in field was at 10-15 days after emergence. Most of the surface sterilant used in tests inhibited the isolation of R.solani from diseased tissue. Anomalous conditions of temperature, light and soil moisture easily usually interfered with the results of the etiological study.