This paper studied the affects of 7 kinds microbiological agents on watermelon seedling growth and the control effect on Fusarium wilt by the method of seedling inoculation．The results showed that S1，S4 and S6
treatments could significantly promote watermelon growth．Their indexes of plant height，stem diameter，fresh
weight above ground，root-crown ratio，strong seedling index，etc．were all higher than that of the contrast．
Biological agents had certain control effects on Fusarium wilt of watermelon．Compared with the respective
contrast，the disease index of‘ Zaojia 8424’ decreased 76.2-92.8，that of‘ Xinong No.8’ decreased 37.0-54.6．
Besides，the disease control effect of these 2 varieties was all outstanding as S6．Further studies found that
Bacillus subtilis could significantly inhibit mycelial growth and spore germination of Fusarium oxysporum f. sp.
niveum race1．Inhibition rate of mycelial growth reached 67.75% and the conidia germination number was only
24.4% of the contrast．The successive control on pathogenic bacteria could reach 49.3%．In summary，S6 has the
best combination effect on watermelon growth promotion and control of watermelon Fusarium wilt．And its strain
has significant inhibitory effect on growth and spore germination of Fusarium oxysporum f. sp. niveum．