In order to explore the correlation of lower-limb muscle of children with diplegia cerebral palsy, and analyze the influence of spasticity on lower-limb muscle relevance of those children, surface electromyography (SEMG) was used as the source of information. In experiment, both SEMG acquisition and muscle tension test of lower limbs gastrocnemius and anterior tibial muscle of twelve cerebral palsy children were carried out. Then, signals were filtered and root-mean-square disposed by Acqknowledge software, and statistical analysis about those obtained data was carried out using SPSS 19.0. The results show that spasticity bate the relevance of lowerlimb muscle of children with diplegia cerebral palsy. This research may provide a reference for basic research and rehabilitation training of cerebral palsy children.