【Objective】The present experiment was conducted to screen effective medicaments for controlling bacterial fruit blotch （BFB） of grafted watermelon seedlings， and to provide scientific basis for BFB control. 【Method】Seeds of watermelon were soaked in 200 times diluted solutions of 17 different kinds of medicaments， the effectiveness of different medicaments was screened preliminarily by observing rate of BFB incidence on grafted seedlings. Different concentrations and combinations were also used to screen the most effective medicament. 【Result】The rate of BFB incidence on grafted watermelon seedlings， treated by 2% kasugamycin （×100）， was low after 6 d of grafting which could selected for the future test. After 12 d of grafting， the rate of BFB incidence was recorded as 1.0， 36.7， 94.3， 95.7 and 98.1% in grafted watermelon seedlings treated with 100， 200， 300， 400 and 500 times diluted kasugamycin （2%）， respectively. The BFB incidence rate of grafted watermelon seedlings was 1.0-2.4% in 12 d after grafting after the watermelon seeds were treated with 200 times of 2% kasugamycin + Lewubing， 72% streptomycin and 72% embamycin （×800）. Dry seed soaking of same medicament resulted in only 0.5-5.7% rate of BFB incidence in variety Xinhongbao， while it was 8.1-11.4% in seedless variety Xinyihao. Seed soaking with 2% kasugamycin （×200） + Lewubing， 72% streptomycin and 72% embamycin （×800） resulted in 1.0-2.4% rate of BFB incidence after 12 d of grafting. Dry seed soaking in 2% kasugamycin （×400） + Lewubing， 72% streptomycin and 72% embamycin （×1000） resulted in 1.0-2.0% BFB incidence rate in seeded grafted watermelon seedlings， while it was 6.7-9.5% in seedless grafted watermelon seedlings. 【Conclusion】The treatment with 400 times of 2% kasugamycin or its combination with other germicides may be recommended to as first powerful medicament for controlling BFB of grafted watermelon seedlings.