Abstract: In order to clarify the field control efficacies of two kinds of composite biocontrol agents against tobacco black shank disease and fusarium root rot disease in tobacco fields, the incidences of tobacco black shank disease and fusarium root rot disease in tobacco fields after applying the two biocontrol agents (A. the mixture of Pseudomonas and Trichoderma viride zymotic fluids at the volume ratio of 1∶1, B. the mixture of Bacillus and Trichoderma harzianum zymotic fluids at the volume ratio of 1∶1) were investigated. The agronomic trait indexes and the contents (mass fraction) of routine chemical components in aerial parts and roots of cured tobacco leaves were measured. The results showed that the composite biocontrol agent A reduced the incidence and disease index of tobacco rhizome diseases, and its relative control efficacy reached 48.46%. Both agents A and B improved the agronomic traits of tobacco plants, increased root fresh weight, root volume and the numbers of lateral roots and fibrous roots. The contents of chemical components in tobacco leaves treated with the two biocontrol agents were appropriate and their proportions were more harmonious.