Great span length makes a suspension bridge very flexible and this feature results in very sensible responses to wind loads. Hence, to investigate structural characteristics of a suspension bridge subject to wind loads more precisely, geometric nonlinear analysis becomes indispensible. In addition, it tends to change configuration and / or fixing method of main cable in recent suspension bridges. Accordingly, existing conventional methods are not proper to analyze new types of suspension bridge which follow these trends and to investigate the three dimensional complicated behavior between structural members of suspension bridges. This study suggests a three dimensional finite element method that can overcome aforementioned problems. All sources of geometric nonlinearity are considered. Structure-wind interaction problems are solved in time domains. Examples for the mathematical model of actual bridge are presented. It is found that this flexible structure is highly nonlinear under design wind velocity.