The purpose of this study was to evaluate the influence of respiratory capacity(forced vital capacity), EMG of rectus abdominal muscle, phonation by respiratory muscle strengthening exercise in children with spasticity cerebral palsy. 24 children with spasticity cerebral palsy was randomized in 2 groups, respiratory muscle strengthening exercise and contro group. In the exprimentral groups, respiratory muscle strengthening exercise for 30minutes duration 3 time per week for 8weeks were respectively preformed, Control group was not performed. Before and after experiments, respiratory capacity(forced vital capacity), EMG of rectus abdominal muscle and phonation was measured in all children. In comparison of difference before and after experiment, the respiratory capacity(forced vital capacity) of respiratory muscle strengthening exercise group was significantly increased than the control group(P<.05), rectus abdominal muscle EMG of the respiratory muscle strengthening exercise group was significantly increased more than the control group(P<.05) and MPT of the respiratory muscle strengthening exercise group was significantly increased more than the control group(P<.05). We found that the respiratory muscle strengthening exercise is useful to improve the respiratory capacity and phonation in children with spasticity cerebral palsy.