Objective To evaluate the serum rocalcitonin(PCT) determination in the diagnosis of emergency patients with fever . Methods 120emergencypatientswithfeverwereenrolledinthestudy,whoseserumsamplesweretestedbyusingelectrochemilu‐minescence immunoassay for PCT concentrations ,at the same time white blood cells(WBC) count and C reactive protein(CRP) were also determined .Bacterial culture results were used as gold standard for the diagnosis of bacterial infection .WBC>10 .0 × 109/L,CRP>10mg/L,PCT>0.5μg/Lwerethejudgmentcriteriafortheevaluationofthoseindicators.Results 73casesofpatients′bacteria culture results were positive ,47 patients′bacteria culture results were negative;63 cases of patients were with PCT ,WBC and CRP levels elevated at the same time;2 patients′WBC count elevated ,while PCT and CRP concentrations did not ;6 patients′serum PCT concentrations increased ,while WBC and CRP levels didn′t ;4 patients′serum PCT and CRP concentration increased , while WBC count didn′t ;35 patients′PCT ,WBC and CRP kept at low levels .Conclusion Serum PCT concentration could be used as an auxiliary diagnosis indicator in the diagnosis of emergency patients with fever .