Objective The aim of this study was to analyze the mechanism of degenerative spondylolisthesis (DS) through measuring vertebra arch angle and facet joint degeneration with 64-slice spiral computed tomography (CT). Methods One hundred and six patients complained of lumbodynia were examined with 64-slice CT. In 28 of 106 patients have lumbar spondylolisthesis, while the other 78 cases have not. The vertebra arch angles of all cases were measured and the facet joint degenerations were analyzed. Results L4--5 vertebra arch angle in DS group were 119. 0°±2. 2°(left) and 118. 8°±1.9° (right) ,respectively. L4--5 vertebra arch angle in control group were 102.9°±1.2°(left) and 104. 7°± 1.2° (right) ,respectively. The joint angle in DS group were 41.1°±1.2°(left) ,and 29.0°±1.2°(right), respectively. The joint angle in control group were 45.5°±2. 1°(left), and 45. 1°±1.2°(right), respectively. There were significant differences of L4--5 vertebra arch angle and more serious of facet joint degeneration( P < 0. 05 ). Conclusion L4 vertebra arch inclination and facet joint degeneration were important to diagnosis of spondylolisthesis.