Abstract: Effect of medium pH, spore number and other factors on the submerged fermentation of the FJAT-9040 strain of Trichoderma harzianum and the inhibition activities of the resultant fermentation liquid and sterile supernatant on the strain FJAT-135of Fusarium oxysporum were investigated.The submerged fermentation was carried out in a 50Lautomatic fermentation vessel.Fermentation duration, pH, viscosity, spore count and dry mycelia weight were altered to study their correlations.The results showed that, during the fermentation, (a) the pH decreased initially but slowly increased after 32hours; (b) the viscosity showed an increase-decrease-increase trend and followed by a decline toward the end; (c) the spore count decreased firstly, increased at the mid-stage, and remained constant at the end;and (d) the dry mycelia weight increased stepwise to reach 10.29mg·mL-1at the end.Except between pH and viscosity, there were significant correlations between pH and spore count, between pH and dry mycelia weight, between viscosity and spore count, between viscosity and dry mycelia weight, as well as between spore count and dry mycelia weight.The optimum duration for the fermentation was 96-108hours.At different culture stages, all fermentation products were effective in inhibiting the growth of FJAT-135at a rate above 77.92%.On the other hand, the sterile supernatant of the fermentation liquid was not found to have the inhibiting effect.The results obtained from this study provide the basic information for the development of a costeffective submerged fermentation process of FJAT-9040.