Background: Chronic Mechanical Low Back Pain (CM-LBP) represents a significant public health problem and an economic burden to employers. There is a gap in literature concerning the investigations on changes of the motor nerve excitability during rehabilitation of lumbar lordotic curve which represent a major barrier preventing the exploration of the most effective conservative treatment on restoring the lumbar lordosis. The Denneroll is a relatively new sagittal plane orthotic device designed to passively stretch the lordotic curve into a more lordotic position. Aim of Study: This study designed to study the effect of lumbar Denneroll traction on motor nerve excitability on chronic low back pain patients. Material and Methods: Thirty patients had participated in this study; they were assigned randomly into two groups (A) experimental group, and (B) control group. Group (A) consisted of 15 patients; they received combined program of Denneroll traction and conservative physical therapy treatment. Group (B) which consisted of 15 patients; they received the same conservative treatment as group (A) in form of (ultrasonic therapy, infrared and stretching exercise). Treatment was given 3 times per week, each other day, for ten consecutive weeks. Patients were evaluated pre-treatment and posttreatment for the H-reflex, H/M ratio and Absolute Rotatory Angle (ARA). Results: Using repeated measures multivariate analysis of variance (MANOVA) test, patients showed significant improvement in the combined dependent variables in both groups but between groups difference group (A) showed a more significant improvement than group (B) in the combined dependent variables. Both of the Denneroll and traditional treatment had a significant effect onthe H-reflex, H/M ratio and absolute rotatory angle indicated that there were significant effects of the tested group (the first independent variable) on the all tested dependent variables; H-reflex, H/M ratio and ARA (F=31.357, p=0.0016). However, there were significant effects of the measuring periods (the second independent variable) on the tested dependent variables (F=114.404,