In view of the high computational complexity in the current delay-dependent stability analysis methods for power grid frequency control systems, a stability analysis method has thus been proposed with a lower computational complexity and lower conservatism. Firstly, in response to the problem of high computational complexity caused by the high dimensionality of the system matrix in the frequency control of power systems, model reconstruction technology is used to reduce the system matrix’s dimensionality, thus achieving the goal of reducing computational complexity. Secondly, in view of the problem of an excessive use of state variables in current analysis methods for time-varying delay power system frequency control, which leads to high dimensions and computational complexity, a delay-dependent stability analysis method has been proposed for frequency control systems based on free matrix integral inequalities, thus obtaining a linear time-varying delay-dependent stability criterion with lower dimensions and computational complexity. Finally, on the basis of the single area load frequency control system, it has been verified that the propsoed analysis method is characterized with a higher calculation efficiency but a lower conservatism.