The invention provides a vertical returning trajectory design method for a sub-stage of a carrier rocket. The method comprises: according to flight characteristics of a sub-stage of a carrier rocket, determining a vertical returning launching point or each sub-flight-phase of a vertical returning preset target position, using a three-freedom-degree kinetic model of a sub-stage vertical returning process on an earth spherical model, to generate a vertical returning ballistic trajectory, wherein each sub-flight-phase from sub-stage separation to sub-stage landing includes a posture alignment stage, a deceleration turning stage, a gliding stage, a power deceleration stage, a pneumatic deceleration stage, a vertical dropping stage, or a gliding posture alignment stage, a power deceleration stage, a deceleration stage, and a vertical dropping stage, the kinetic model being determined by flight speed, a trajectory inclination angle, a trajectory rotation angle, speed and position components in a launching coordinate system, an attack angle, a sideslip angle, and a variable thrust factor. The invention also provides a vertical returning trajectory design method for a carrier rocket booster stage and a carrier rocket. The vertical returning trajectory design methods are simple in operation and easy in engineering implementation. Track indexes of each obtained sub-flight-phase satisfy constraint requirements of heat flux peak, dynamic pressure, flight overload, and terminal positions.