Purpose : The purpose of this study is to compare muscle activations of neck, trunk and leg in cerebral palsy of spastic diplegia with genu recurvatum and knee flexion contracture, when using anterior and posterior walkers. Methods : We selected 21 cerebral palsy and received the written consent to participate in this study. The inclusion criteria for participation required patients to have spastic diplegic CP; to be between 3~6 years of age, to have a GMFCS III grade, to have no botulinum toxin injection and orthopedics surgery within before six months starting the study. Measurements of muscle activities (sternocleidomastoid, splenius capitis, rectus abdominis, erector spinea, gluteus maximus, rectus femoris, medial hamstring and calf muscles) were evaluated anterior and posterior walker ambulations. Statistical evaluation of these data were accomplished by utilizing the paired t-test and independent t-test by SPSS 20.0 program. Significance level was set at p<.05. Results : The following results were obtained. There was significant difference on muscle activation of neck, trunk and legs(soleus except) in anterior and posterior walkers. There was no significant difference in muscle activation of neck but significant difference in muscle activation of trunk, legs between genu recurvatum and knee flexion contracture(rectus abdominis, medial hamstring when using anterior walker, rectus abdominis, erector spinea, gluteus maximus, medial hamstring when using posterior walker). Conclusion : The conclusion of this study is the different knee joint forms would have different effect on muscle activation of trunk and legs while cerebral palsy of spastic diplegic ambulated with anterior walker and posterior walker.