To study the role of outer membrane protein A （OmpA） in the pathogenicity of Elizabethkingia miricola， the ompA gene mutant strain （△ompA） was constructed via homologous recombination using E. miricola FL160902 as the wild type strain. Subsequently， the growth characteristics， biofilm formation， serum survival ability， adhesion ability， bacterial colonization of the wild strain and △ompA， as well as their pathogenicity to frogs were analyzed. The results showed that there was no significant difference in growth characteristics and survive ability in frog serum between △ompA and wild strain. However， compared with the wild strain， the biofilm formation capacity of △ompA increased by 66%， and the adhesion capacity of △ompA to bEnd.3 cells decreased by 61%. The results of animal experiment showed that the average bacterial load of △ompA in the blood， spleen and brain of infected frogs were （3.15×10⁸±0.09×10⁸）， （2.11×10⁸±0.07×10⁸） and （6.61×10⁸±0.16×10⁸） copies/g， respectively， which were significantly lower than that of the wild strain infected frogs （P<0.05）， and the lethality rate of frogs infected with △ompA was 37%， which was significantly lower than that of the wild strain （75%）. The results indicated that ompA deletion did not change the antiserum killing ability of E. miricola， but increased the biofilm forming ability of E. miricola， reduced its adhesion ability and decreased its pathogenicity to frogs.