Objective To observe influence of continuous lumbar cistern drainage on levels of amyloid β-peptide (Aβ) subtype (Aβ1-42) in cerebrospinal fluid and plasma in patients with diffuse axonal injury (DAI) and investigate its clinical significance.Methods Eighty-one DAI patients were enrolled and randomized into treatment group (42 cases) and control group (39 cases).Patients in control group received simple conventional therapy,while the patients in treatment group received not only conventional therapy but 14 days of continuous lumbar cistern drainage.Levels of Aβ1-42 in cerebrospinal fluid and plasma were detected by ELISA assay before therapy and at 1,5,9,and 14 days after therapy.Prognosis was assessed using GOS at 6 months after therapy.Results Levels of Aβ1-42 in cerebrospinal fluid and plasma showed a decrease in the first place and a gradual decrease afterwards in both groups,but a bigger and earlier drop of Aβ1-42 levels was observed in treatment group.Two groups showed significant difference of Aβ1-42 levels at day 14 (P ＜ 0.05).At 6 months after therapy,GOS score between treatment and control groups was (4.1 ± O.5) and (3.4 ± 0.3) points respectively (P ＜0.05).Conclusion Continuous lumbar cistern drainage improves the prognosis of DAI and this may relates to the decrease of Aβ1-42 levels in cerebrospinal fluid and plasma.