This paper proposes an analysis method for the static mechanics of suspension bridges based on segmental catenary and FEM software. A comparative research on mechanics of suspension bridge with a span of 2 000~5 000 m is conducted according to the proposed method，and CFRP suspension bridges are proved advantageous and practicable. A parametric study for the deflection performance of 2 000 m CFRP suspension bridge is executed in order to enhance its stiffness，where the span arrangement，rise to span ratio，side to main span ratio，inertia of girder and tower，and the central buckle are considered，respectively. A serials of design suggestions for improving the structural stiffness are proposed.