Abstract: The floor response spectrum of the eccentric structure subjected to two-dimensional horizontal earthquake input is computed on SIMULINK emulator, and a few influential key parameters are also discussed. In the end the shortcomings of the SRSS (Square Root of the Sum of Squares) method used in the current seismic design code are indicated. The results show that with the subsystem’s mass varying the floor response spectrum changes significantly at the tuned frequency, and less significatnly at the earthquake dominant frequency. The floor response spectrum is varied with different damping ratios of the eccentric structure and the subsystem. Furthermore, spatial locations of the subsystem influence the floor response spectrum, so does the eccentric distance of the eccentric structure. The latter is more complicated. The floor response spectrum obtained according to the design specifications is not proper in the peak-value region, and it is proper outside the peak-value region if the multi-directional coupling phenomenon is not significant.