Abstract: In order to investigate the main viruses causing tobacco viral diseases in main tobacco-growing areas, 266 tobacco leaf samples with viral disease symptoms collected from part of the tobacco-growing areas in Chongqing, Sichuan, Yunnan, Guizhou, Henan, Sha'anxi and Gansu were tested by antigen direct coated enzyme-linked immunosorbent assay(ELISA).Tobacco mosaic virus(TMV), Cucumber mosaic virus(CMV), Tomato mosaic virus(ToMV), Turnip mosaic virus(TuMV)and Potato virus Y(PVY)were detected.The infection percentage(75.56%)of PVY was the highest, and that of TMV, CMV, ToMV and TuMV was 65.41%, 57.14%, 36.84% and 34.59%, respectively.ToMV and TuMV were detected only in the samples from Yunnan, Sichuan, Guizhou and Chongqing.Of the 257 positive samples, 97 cases were infected by CMV(7.39%), TMV(13.23%)or PVY(17.12%)alone.Other positive samples were infected by two or more viruses and about 55.63% of them were infected by all the five viruses.Tobacco samples in the field showed complex viral disease symptoms.These results indicated that viral mixed-infection occurred seriously in field tobacco and PVY has become a dominant virus in some tobacco-growing areas.