Objective To observe the effect of ultra-low frequency transcranial magnetic stimulation on cerebral blood flow in children with spastic diplegia cerebral palsy. Methods 36 cases of spastic diplegia cerebral palsy were divided into control group (n=21) and obsevation group (n=15), 19 healthy children were as normal group. The control group received conventional rehabilitation training. The obsevation group received the ultra-low frequency transcranial magnetic stimulation in addition. All the children received the check of transcranial color Doppler (TCD). Results Several arterials flow velocity was lower, several arterials pulsatility index and resistance index were higher in the obsevation group than in the normal group before treatment (P<0.05). Compared with the control group, the arterial flow of obsevation group improved, pulsatility index and resistance index decreased in some degrees in the obsevation group after treatment (P<0.05). Conclusion The cerebral blood flow is of low velocity and high resistance in spastic diplegia children, while ultra-low frequency magnetic stimulation could improve the condition of cerebral flow.