Objective To study the in vitro antimicrobial susceptibility testing results of fosfomycin (FOS) combined with other antimicrobial agents against multidrug-resistant Pseudomonas aeruginosa (MDR-PA), and provide guidance for clinical combination antimicrobial use. Methods Patients with healthcare-associated pneumonia (HAP) and admitted to the department of critical care medicine of a hospital from January 2018 to December 2019 were selected, 50 strains of MDR-PA were screened out by microbiological laboratory, antimicrobial susceptibility testing was performed with agar dilution combined with disk diffusion method, fosfomycin (FOS)-containing agar plates were prepared, with antimicrobial concentrations of 50, 100, 150, 200 and 250 μmg/L respectively; disks containing piperacillin/tazobactam, ceftazidime, meropenem, amikacin, and ciprofloxacin were pasted on the antimicrobial-containing plate for routine culture. Results FOS had no synergistic effect with piperacillin/tazobactam and ceftazidime (both P>0.05), but had synergistic effect with meropenem, amikacin and ciprofloxacin (all P < 0.05). Comparison of FOS+ meropenem combination and FOS+ ciprofloxacin combination, difference was not significant (both P>0.05); comparison of FOS+ meropenem combination and FOS+ amikacin combination, difference was significant (P < 0.05); comparison of FOS+ ciprofloxacin combination and FOS+ amikacin combination, diffe-rence was significant (P < 0.05). Conclusion For MDR-PA, FOS has synergistic effect with meropenem, amikacin and ciprofloxacin, the synergistic effect of FOS+ meropenem combination and FOS+ ciprofloxacin combination is better than that of FOS+ amikacin combination.