Objective To observe the changes and clinical significance of procalcitonin(PCT) level in children with bacterial pneumonia.Methods The levels of PCT,hs-CRP and WBC were detected in 31 pneumonia children pre and post antibiotic treatment,and the changes were observed.Results The PCT levels of the 31 patients were all increased before treatment.After cured,PCT level of 28 cases returned to normal.But in the 28 normal cases,WBC level increased in 10 cases(35.7％),and hs-CRP level elevated in 4 cases(14.3％).In the other 3 cases,the PCT levels decreased from 5.69ng/mL,1.25ng/mL and 0.83ng/mL at admission to 0.51ng/mL,0.55ng/mL and 0.52ng/mL,respectively.And in these 3 cases,there was one case with the levels of WBC and hs-CRP respectively ascended,in which WBC level descended from 13.1 × 109/L to 12.1 × 109/L and hs-CRP level reduced from 20.92mg/L to 7.38mg/L.Conclusion The sensitivity of the index PCT is the highest at the accurate time phase of bacterial pneumonia,which can guide the reasonable use of antibiotics.