Objective To investigate the guidance value of procalcitonin(PCT) dynamic measurement on antibiotics usage of patients with stroke associated pneumonia(SAP).Methods One hundred and thirty-two cases with SAP were randomly divided into control group(64 cases with regular treatment) and observation group (68 cases with procalcitonin dynamic monitoring treatment).The treatment course of antibiotics in control group was according to antibiotics guidelines in China.Patients in observation group were given antibiotics for 5 days,stopped if the level of PCT was less than 0.25 μg/L,and continued to take if the level of PCT was more than 0.25 μg/L.The information were recorded including periods and cost of antibiotics usage,the periods and costs of hospitalization,clinical efficacy,mortality on the 30th day.The score of Institutes of National Institutes of Health Stroke Scale (NIHSS) and Barthel index (BI) were measured.Results (1) There were no significant differences in terms of age,gender,hypertension rate,coronary heart disease rate,diabetes rate,systolic blood pressure,the score of NIHSS in admission,pathogen and antibiotics between two groups (P ＞ 0.05).(2) After 30 days treatment,there were no significant differences in terms of clinical efficacy(86.8％ (59/68) vs.87.5％(56/64)),mortality (7.4％ (5/68) vs.7.8％ (5/64)),the score of NIHSS ((12.3 ±5.8) vs.(11.7 ± 4.5)) and BI (60.9 ± 22.3 vs 58.7 ± 21.6) between observation group and control group (P ＞ 0.05).The periods of hospitalization in observation group was (20.1 ± 5.1) d,less than that of control group ((25.4± 6.0) d,t =5.479,P ＜ 0.01).The costs of hospitalization in observation group was (8 ± 6) thousand yuan,significant lower than that of control group ((12 ± 8) thousand yuan,t =3.262,P ＜ 0.01).The periods of antibiotics usage in observation group was (11.3 ± 2.6) d,less than that of control group ((14.4 ± 3.1) d,t =6.238,P ＜ 0.01).The costs of antibiotics in observation group was (3 ± 1) thousand yuan,significant lower than that of control group ((5 ± 2) thousand yuan,t =7.331,P ＜ 0.01).Conclusion PCT dynamic monitoring can guide the safe usage of antibiotics in SAP in terms of shortening the length of hospitalization,duration of antibiotics,and reducing the costs.