According to the standard for the GSM for railway（GSM-R） wireless systems in China train control system level 3（CTCS-3）,the control data transfer delay should be no larger than 500 ms with greater than99% probability.Coverage of both non-redundant networks and intercross redundant networks and cases of single Mobile terminals（MTs） and redundant MTs on one train are considered,and the corresponding vehicle-ground communication models,delay models,and fault models are constructed.The simulation results confirm that the transfer delay can meet the standard requirements under all cases.In particular,the probability is greater than 99.996% for redundant MTs and networks,and the standard of transfer delay in CTCS-3 will be improved inevitably.