Objective To investigate the changes of antimicrobial peptide LL-37 and C-reactive protein (CRP ) in the patients with Pseudomonas aeruginosa positive sputum culture and their mutual relation . Methods Fifty cases of Pseudomonas aeruginosa positive sputum culture and 27 cases undergoing physical ex-amination in the Guangdong Provincial Hospital of Chinese Medicine from September 2016 to May 2017 were selected as the research subjects .The level of antimicrobial peptide LL-37 was detected by double antibody sandwich ELISA and the CRP level was detected by immunoturbidimetry .Results The levels of antimicrobial peptide LL-37 and CRP in the Pseudomonas aeruginosa positive sputum culture group were significantly high-er than those in the healthy control group ,the difference was statistically significant (P< 0 .05) ,and they showed the positive correlation (r=0 .411 ,P<0 .05) .Conclusion In positive sputum culture of Pseudomonas aeruginosa ,antimicrobial peptide LL-37 and CRP levels are increased ,which has a certain clinical application value for the early diagnosis of infection .