Objective To determine the optimal injection dose of ozone for the treatment of lumbar intervertebral disc protrusion.Methods A total of 240 patients with lumbar intervertebral disc protrusion were randomly and equally divided into four groups,with 60 patients in each group.Under CT guidance intervertebral injection of ozone was performed.The injection dose of ozone(50 ug/ml)used for patients in group A,B,C and D was 10 ml,20 ml,30 ml and 40 ml respectively.Immediately after the procedure CT scanning was made to check the result. A follow-up lasting 6-12 months was carried out.Clinical observation,including the ablation degree of the nucleus puiposus,the therapeutic results and the adverse reactions,was conducted.The results were statistically analyzed and compared among the four groups.Results A significant difference in the therapeutic effect existed between group A(10 ml)and other three groups(P＜0.05),while no significant difference in the therapeutic effect existed among group B(20 ml),group C(30 ml)and group D(40 ml),with P＞0.05.The occurrence of complications was increasing with the injection dose used.Conclusion The optimal injection dose of ozone for the treatment of lumbar intervertebral disc protrusion is 20 ml.