The purpose of this study is to improve the effect of Lumbar extensor exercise program and develop the Lumbar extensor exercise program which will be suitable to the patients characteristics. In this study the experimental group was made up of 38 subjects. They are the patients with low back pain using the Lumbar extension exercise program in C hospital. The lumbar extension exercise program was given two times a week for 8 weeks. The results were estimated by Lumbar extensor strength by diagnosis agent. The results were measured three times, one time pre-treatment and two times post-treatment at 4weeks and 8weeks by lumbar extensor curve angle(0, 12, 24, 36, 48, 60, 72). The results were compared at pre-test 4weeks and 8weeks. The muscle strength measured at both 4weeks and 8weeks with the greater strength was shown at 4weeks. The muscle strength of patients with M.strain, Laminectomy and HNP was increased at all angles except for patients with stenosis. The results of this study indicated that diagnosis influenced the muscle strength in Lumbar extensor exercise program.