Objective: To explore and optimize the settings of alarm in Sysmex UF5000 urinary tract infection (UTI) system to assist the diagnosis of UTI. Methods: A total of 2 871 urine samples were collected and tested by Sysmex UF5000 urine sediment analyzer. The diagnostic accurate rate, sensitivity, and specificity of the default alarm threshold settings of the instrument for UTI were calculated regarding to the clinical diagnosis of UTI. The thresholds of white blood cell count (WBC) and bacterial count (BACT) were optimized to meet the local hospital need. Results: The accurate rate of instrumental alarm settings for diagnosing UTI was 70.61%, with a sensitivity of 94.23% and specificity of 70.61%. At the default setting, the diagnostic sensitivities of WBC (WBC>10/μL) and BACT (BACT>10/μL) were 94.23% and 94.12%, while specificities were 58.02% and 68.98%. The optimal cutoff values for WBC and BACT determined by ROC curve were 24.9/μL and 1 157.3/μL, respectively. However, when sensitivities of WBC and BACT were set as 95%, the specificities of both parameters were 56.8% and 57.01%, yielding the cut-off values as 26.7/μL and 60.1/μL, respectively. Clinical validation showed that best sensitivity and specificity of the system was achieved(sensitivity 93.34%, specificity 71.17%) when the WBC and BACT were reset at 26.7/μL and 1 157.3/μL, respectively. Conclusion: Optimized the alarm threshold of the Sysmex UF5000 achieve higher sensitivity and specificity, assisting rapid diagnosis of clinical UTI.