On the basis of the mechanism of stiffness degradation and torsional divergence in long-span suspension bridges subjected to static wind, two criterions have been reasonably chosen for the evaluation of torsional divergence in smooth flows and turbulent flows, respectively. In a concerned bridge immersed in smooth flows, taking into account the easy estimation of the deformation conformation and the simple evolution rule of main cables, the vertical displacement at the mid-location of main cables was adopted as a criterion to estimate the stiffness degradation and torsional divergence. When the vertical displacement reaches a critical value, the phenomenon of aerostatic torsional divergence will occur. In the case of turbulent flows, however, the bridge structure will experience complicated and stochastic dynamic responses in a form of multiple modal coupling. Consequently, the criterion used in smooth flows is not applicable to this case. To this end, a new criterion based on the identification of the length of the main cables in time domain was put forward. The criterion can be described as that, when the minimum value of the main cable length indentified in the whole time domain reaches the value being equal to or very close to the zero-strain length, the bridge will be affected by the intermittent torsional divergence because of the softening of the main cable subsystem. It is shown that, using some static and dynamic finite element analyses, the phenomena of the aerostatic torsional divergence behavior of long-span suspension bridges in different types of field flows can be well explained with this new criterion.