[Purposes] The accurate determination of the dynamic responses of a multi-lane wide submerged floating tunnel (SFT) under eccentric vehicle loads is a crucial prerequisite for its structural design. [Methods] The tube was equivalenced as an Euler-Bernoulli spatial beam, anchor cables were simulated as multiple discrete elastic supports, and vehicle loads were treated as multi-axle concentrated forces. A theoretical model for the multi-lane wide SFT under eccentric loads was established based on the Hamilton principle. Simultaneously, a numerical simulation model under the eccentric vehicle loads was developed using the ANSYS software. Taking four multi-lane wide cross-sections (elliptical, octagonal, round-ended, and pointed-end) as examples, the influences of boundaries, cross-sectional shapes, eccentricity degree and loading patterns of vehicle loads, on the dynamic response were analyzed using both methods. [Findings] Hinged boundaries with weaker constraints release end rotations, leading to increased vertical deflection at the mid-span. The elliptical section exhibits the smallest vertical displacement and rotation angle. The round-ended section shows the smallest lateral displacement and bending moment but a relatively larger rotation angle. The octagonal section has the largest lateral displacement and peak negative bending moment. The pointed-end section"s performance fell between the three. Shear force and torque are less sensitive to cross-sectional changes. Greater eccentricity of vehicle loads results in larger lateral displacement, rotation angle, bending moment, and torque. Opposing traffic patterns altered the distribution law of responses along the span (shifting from a single peak at mid-span to double peaks on both sides). [Conclusions] The findings provide theoretical references for the cross-sectional selection and refined design of multi-lane wide SFTs.