Objective To investigate the effect of the quorum sensing（QS） system LuxR type regulator abaR on the pathogenicity and drug resistance of Acinetobacter baumannii. Methods The abaR-knockout（ΔabaR） strain of A. baumannii ATCC 17978 was constructed，and the growth curve analysis，serum killing experiment，and biofilm formation assay were used to compare the wild strain and the ΔabaR strain in terms of growth rate and serum killing ability. The multi-step in vitro drug resistance induction test was used to investigate the differences in the expression levels of related drug resistance genes after induction of drug resistance between the ATCC 17978 wild strain and the ΔabaR strain. Results The growth curve showed that there was no significant difference in A_{600 nm} value between the wild strain and the ΔabaR strain at each time point（t=10.720，P>0.05）. The serum killing experiment showed that the ΔabaR strain had a significantly lower normal human serum/phosphate buffered saline（NHS/PBS） ratio than the wild strain（t=3.968，P<0.05）. The biofilm formation assay showed that the ΔabaR strain had a significantly lower biofilm formation ability than the wild strain within the first 24 hours of culture（t=4.632，P<0.01）. After the wild strain and the ΔabaR strain were induced to meropenem-resistant strains in vitro，compared with the wild strain，the ΔabaR strain had significantly lower expression levels of the drug-resistance genes AdeA，AdeB，and AmpC（t₁=11.330；t₂=15.010；t₃=13.420，P<0.001）. Conclusion The abaR gene significantly influences the virulence and acquired resistance of A. baumannii by regulating biofilm formation and the expression of efflux pump genes. Interference with the abaR receptor molecule within the QS may be an effective strategy to inhibit QS signaling and address the drug resistance of A. baumannii，which lays a foundation for developing novel antibiotics for the treatment of drug-resistant strains.