Objectives : In these days Low back pain is most common, and the weakness of muscle strength is important factor. The aim of this study is to prove the influence of the exercise therapy on pain control and muscle strength in acute low back pain patient. Methods : Subjects of this research were 30 inpatients with acute low back pain from 2008. 3. 20 to 2008. 6. 20. 15 patients in each, 2 groups; Non exercise therapy, exercise therapy were divided and the conclusions for treatment are as follows. Results : 1. Regarding alleviation of pain by VAS, both non exercise therapy Group I and exercise therapy Group II showed significant decrease of VAS. 2. Muscle strengthening by extension and flexion peak torque, the exercise therapy Group II showed higher rate of improvement than the non exercise therapy Group I in extension peak torque. 3. Muscle strengthening by extension and flexion peak torque ratio, the exercise therapy Group II showed higher rate of improvement and distribution approach to normal ratio than the non exercise therapy Group I. Conclusions : Exercise therapy was effective in muscle strengthening of acute low back pain.