Abstract: Objective To detect the concentration of interleukin-4（IL-4） in gingival crevicular fluid（GCF） in the patients with chronic periodontitis before and after treatment, to research the relationship between IL -4 in GCF and periodontitis and the effect of IL-4 in pathogenesis of periodontitis and its progressiveness. Methods The concentration of IL-4 in GCF were detected by way of enzyme-linked immunosorbent assay following careful sampling of GCF with the standardized filter strips in healthy adults as well as periodontitis patients. Results The concentration of IL-4 in GCF in the inflammatory group was significant lower than the normal group（P＜0.05）. No significant deference of IL-4 concentration and statistical significance were found before and after a month′s treatment（P＞0.05）. Negative correlation was found between probing depth and the concentration of IL-4 in GCF, while the concentration of IL-4 in GCF was not significantly associated with the clinical parameters gingival index and attachment loss. Conclusion Deficiency of IL-4 can result in periodontitis and the examination of IL-4 in GCF might be used as a sensitive diagnosis index of periodontitis at early stage.