<p>The determination of the steady configuration of flexible spacecrafts in the challenging space environment holds paramount importance for the prediction of structural mechanical behaviors and the monitoring of failures during in-service conditions. In this paper, based on the nonlinear Euler-Bernoulli beam model, the differential equations describing the steady configuration of an ultra-large spacecraft are transformed into polynomial equations by introducing the moment integration function and Taylor expansion, facilitating rapid and accurate solutions. Furthermore, accounting for the additional moment effect induced by axial component of the gravity-gradient force, the steady configuration under all loads is iteratively calculated starting from the equilibrium configuration under normal loads, resulting in a novel integral and iterative solving method under the combined action of gravity-gradient force and thermal load. Based on the above method, an empirical formula for the steady configuration involving multiple parameters is developed to solve the problem of rapid and accurate prediction of static configurations of large-scale spacecraft under different assembly states. The numerical results show that the proposed method can obtain highly accurate and stable solutions with only a few iterations. Additionally, it sheds light on the impact of spacecraft configuration asymmetry in the space force-thermal environment. Parameter analysis reveals that increasing the spacecraft’s length significantly amplifies the geometric nonlinearity of the structure, and adjusting the spacecraft’s attitude effectively constrains its deformation in the face of force-thermal conditions.</p>