Dynamic stability of suspen-domes is analyzed in the paper. Theoretical investigation is conducted based on the Lypumov dynamic stability theory. Based on B-R criterion, an improved method to evaluate the dynamic stability of suspen-domes is proposed. According to the method and time-history response curves, the dynamic stability of the suspen-domes is evaluated under horizontal seismic excitations. The dynamic stability characteristics, stability mode and cable mechanical behavior of the suspen-domes with different rise-span ratios are analyzed. The results show that the effect of the rise-span ratios on the dynamic stability is different. When the exciting acceleration approaches the critical point, some cables may relax, but they may be tensed again.