The invention discloses a determining method and device for a radio block center (RBC) control train number calculation parameter. The determining method comprises the steps that statistics on the maximum simultaneous use condition within the jurisdiction range of an RBC from a station to a departure line at the same moment is conducted; according to the character of the station, the operation organization characteristic and the passed car ratio of the station, by referring to the maximum simultaneous use condition, obtained through statistics, from the station to the departure line, fitting analysis is conducted on the maximum simultaneous use ratio from the station to the departure line through normal distribution, and the value of the utilization factor k is determined while a station track of a CTCS-3 level motor train set can be stored within the control range of the RBC used for calculating the control train number; and/or according to train operation direction information and a track blocking system, the number T of the switching position within the control range of the RBC and the control range of an adjacent RBC is determined. The RBC control train number calculation parameter can be better determined, and the accuracy and effectiveness of control train number calculation are improved.