Objective To observe the protective effect of Hyssopus officinalis L. pretreatment on asthmatic mice and explore its possible mechanism. Methods Thirty two Balb/c mice were randomly divided into 4 groups: control group, asthma group, dexamethasone group and Hyssopus officinalis L.  group, with 8 mice in each group. Except for the control group, the other three groups made asthma models. In asthma group, 0.2 ml sensitizing solution was injected intraperitoneally on the 1st and 15th days, and 1% ova solution was inhaled on the 22nd day, 30 minutes each time, three times a week for 8 weeks. Dexamethasone (0.005mg/10g) and extract (004g/10g) were given by gavage one hour before OVA challenge in dexamethasone group and shenvanilla group, respectively, once a day for 8 weeks. The control group was treated with normal saline instead of ova. After 8 weeks, samples were taken and the expression of BCL-6, CXCR5,ICOS, ICOSL and IL21 mRNAs in lung tissues were detected by real time PCR. Results Compared with the asthmatic group, the percentage of CD4+CXCR5+/CD4+, CXCR5+ICOS+/CD4+CXCR5+,ICOS+/CD4+CXCR5+ and the expressionsof BCL-6, CXCR5, ICOS, ICOSL and IL-21 mRNA in lung tissues were significantly decreased in Hyssopus officinalis L. group (P＜0.05).Conclusion Hyssopus officinalis L. may play a therapeutic role in chronic asthma by reducing the number of Tfh cells and affecting the expression of related molecules.