Structural deformation caused by live loads is a major concern in the design of multispan suspension bridges. Deformation characteristics of double-cable multispan suspension bridges are the focus of this paper. The authors propose a simplified mechanical model of the double-cable multispan suspension bridge for static analysis. Analytical formulas for calculating maximum deflection of the girder in a loaded span were deduced on the basis of the mechanical model. Finite-element models were established to verify formulas, and a comparison of formulas with FEM analysis revealed excellent agreement. The effects of major design parameters on the deformation of double-cable multispan suspension bridges were also studied. Research shows that the distribution of dead loads to the top and bottom cables had little effect on deformation. The sag-to-span ratio of the main cable imposed a significant effect on deformation, and structural deformation decreased with a decrement in top-cable sag or an increment in bottom-cable sag. A comparison was made between double-cable multispan suspension bridges and traditional multispan suspension bridges regarding deformation. The results indicated that with the same tower stiffness, the deformation of a double-cable multispan suspension bridge was far less than that of a traditional multispan suspension bridge.