Purpose : The purpose of this study is change of lumbar multifidus muslce recorded simultaneously by ultrasound imaging during upper extremity functional movement in chronic low back pain patients. The subject were consisted of 10 women patients with chronic low back pain and healthy asymptomatic subject 10 women. Methods : 10 women patients with chronic low back pain and healthy asymptomatic subject 10 women is voluntary participated for the research. Subjects were positioned in standing. Multifidus size were measured from L4 vertebral segement. The ultrasound imaging apparatus(Sonoace 6000, Medison, Korea) was epuipped with a 5-MHz convex array transducer. The upper extremity lifting movement used to activate the multifidus was then measured. Results : Results of the analysis showed that at the L4 vertebral leves, healthy asymptomatic subjects had significantly larger multifidus muscle compared with chronic LBP subjects. Conclusion : This study will be used as treatment method of patient with chronic LBP. The multifidus muscle in chronic LBP patients clinical significance. Most of chronic LBP patients have multifidus contraction pattern. Especially multifidus contraction in L4 vertebral segement. So chronic LBP patients necessary multifidus muscle release treatment.