Power system stabilizer design for multi-machine power systems is studied in this paper. The difficulties of applying some existing design methods to stabilizers for day-to-day commercial operation are first discussed from the practical application point of view. Then it is shown that, whereas the design problem can be conveniently formulated as a large-scale decentralized system stabilization problem, it can also be translated into an equivalent one of feedback controller design for a multi-input multi-output system. A frequency-response-based sequential loop-closure method is suggested for the design and it is applied to a model of a 10-machine practical power system and that of a 5-machine sample system. In both cases, the designs lead to a satisfactory system damping performance. The results from computer analysis and simulation, a comparison between the suggested method and another design method proposed by Aldeen and Crusca (1995), and the nature of the suggested method have shown that the new design method may have some advantages in avoiding the practical difficulties discussed, and can also avoid some of the theoretical problems involved in the application of Aldeen and Crusca's method.