Abstract: Objective To research the changes and diagnostic value of procalcitonin(PCT) and C reactive protein(CRP) levels in infectious patients with open fracture of tibia and fibula. Methods Total 93 patients with open fracture of tibia and fibula in our hospital from November 2016 to April 2018 were divided into the infection group(36 cases) and the non-infection group(57 cases). The levels of PCT and CRP were measured 1 day, 3 days, 5 days, 7 days and 10 days after operation, and the clinical value of PCT and CRP in the diagnosis of infection after open fracture of tibia and fibula were analyzed. Results A total of 54 pathogens were isolated from 36 patients with fracture infection. Among them, 33 strains were gram-positive bacteria(61.11%), 18 strains were gram-negative bacteria(33.33%), and 2 strains were fungi(5.56%). There were no significant differences in the levels of PCT and CRP between the two groups 1 day after operation(P>0.05). The levels of PCT and CRP in the infection group were significantly higher than those in the non-infection group 3 days, 5 days, 7 days and 10 days after operation. The PCT and CRP levels of the two groups reached the peak 3 days after operation, and then gradually decreased(P<0.05). ROC analysis showed that the AUC of PCT, CRP, and PCT+CRP were 0.863, 0.813 and 0.912, respectively. The sensitivity, specificity and accuracy of PCT+CRP were 94.44%, 92.98% and 93.55% respectively, which were higher than PCT and CRP(86.11%, 84.21%, 84.95% and 72.22%, 70.18%, 70.97%, respectively). Conclusion The levels of PCT and CRP are closely related to infection after open fracture of tibia and fibula. They can be used as an important index for clinical diagnosis of infection after open fracture of tibia and fibula, and can provide reference for early diagnosis and prevention of infection.