Floating involute splines are widely used in aviation power transmission systems to transmit torque. In this paper, by establishing a finite element model of the dynamic deformation of the floating involute spline shaft, the influence of the dynamic deformation of the spline shaft on the misalignment state of the spline pair under various typical dynamic overloads was analyzed. And a contact simulation model of the floating spline pair with the actual tooth profile was established to study the influence of the spline misalignment caused by dynamic deformation on the contact pressure distribution on the tooth surface. The contact stress fatigue strength of the spline pair under dynamic loads such as limit loads and ultimate loads was evaluated. The results show that the axial overload can lead to the axial movement of the mating surface of the floating spline, reducing the effective axial contact length; the radial overload and gyroscopic moment can lead to the parallel misalignment and angular misalignment of the spline. When the overloads are superimposed, the angular misalignment of the spline is the most significant under the limit load, and the parallel misalignment is the most significant under the ultimate load. There are obvious stress concentrations and uneven load-bearing in the contact stress distribution of the spline under the limit and ultimate loads. According to the infinite life and static strength design methods, the evaluation shows that the long-term working contact fatigue strength of the floating spline of a certain type of engine under the ultimate load does not meet the design requirements, and the spline parameters need to be optimized. The quantitative analysis method for the misalignment of the floating spline under the superposition of various dynamic loads formed in this paper provides an important theoretical reference for the design of the misalignment of the aviation floating spline and the improvement of its long-term working ability.