SummaryTo develop reasonable structural schemes of frame–core tube structures in the preliminary seismic design, a stiffness estimation of the main subsystems, that is, core tube, frame, and outrigger, is provided through the rocking model (RM) and flexural–shear coupled model (FSM). A nonuniform RM (RM‐MS) is proposed with the dual nonuniform distributions of mass and subsystem stiffness corresponding to those of the nonuniform FSM (FSM‐MS). The dynamic properties of the RM‐MS are semianalytically solved with the general solution for the free vibration of the nonuniform flexural beam and the rotational stiffness matrix of outriggers. The relation between the FSM‐MS and RM‐MS is established based on the first two vibration periods and nonlinear fitting and extended to present a subsystem stiffness estimation strategy with target maximum interstory drift ratios (IDRmax) and overturning moment distribution ratios (RM,B). The feasibility and effectiveness of the strategy are fully demonstrated by three cases with different target RM,B. RM‐MS effectively controls structural lateral stiffness of FSM‐MS in advance. With the target RM,B beyond the feasible range, it is necessary to adjust the first two vibration periods estimated by FSM‐MS. Compared with the axial rigidity of frame columns, the flexural rigidity of outriggers shows higher priority to increase RM,B.