Abstract：Objective To explore the values of the dynamic changes of C-reactive protein (CRP) and procalcitonin (PCT) on the diagnosis and treatment of infectious diseases. Methods The levels and dynamic changes of CRP, PCT were monitored and analyzed in 85 infectious patients on the second day admitted to hospital, and the fourth, sixth, eighth, tenth day after received antibiotic treatment. Results The serum CRP and PCT levels in patients were significantly elevated on 2nd day admitted. As the infection under control, the levels of CRP and PCT were gradually decreased. There were significant differences between the second day and the tenth day (p < 0.01). The levels of CRP on 2nd day were significantly increased; PCT levels in 71 cases (83.5%) were increased. Conclusion The results suggest that the specificity of PCT is better, the level of PCT was dropped to normal while the level of CRP was still high in the later period of treatment.