<p>The fork-type electro-hydraulic actuator is the core driving component of the large-diameter marine butterfly valve. Its structural parameters and tolerance design directly affect performance, cost and life. Most of the existing studies are based on ideal geometric assumptions, ignoring the coupling effect of size and shape error, resulting in design redundancy or failure risk. In addition, if the processing accuracy of all parts is blindly improved, the manufacturing cost will be greatly increased. To this end, this paper proposes a parametric finite element-transient dynamics co-simulation framework, which reveals the mechanism of 10 key errors on the contact pressure and stress of bushings for the first time. A static analysis model considering the deflection angle of the guide groove is established and plotted. The butterfly valve opening-output torque curve is obtained, and the influence of multiple structural parameters on the output torque and radial load is quantified. Research shows that compared with the traditional single static model, the proposed method can accurately calculate the stress concentration area under transient conditions. In addition, the coaxiality error has the most significant and lasting effect on the performance of the actuator, and the accuracy of the coaxiality error should be controlled preferentially.</p>