For the traditional large field-of-view (FOV) off-axis reflective optical system, the initial configuration solves only axial aberrations, while the off-axis image quality is poor, and it is difficult to optimize large FOV image quality. Considering the above problems, this paper establishes an initial configuration solution method with joint aberrations of Nodal aberrations and Seidel aberrations. A global simulated annealing algorithm is used to automatically obtain thesolution of the large FOV off-axis reflective initial configuration. As a result, the "positive-negative-positive" initial configuration of the large FOV off-axis three-mirror system is obtained directly, with good image quality in the on-axis and off-axis FOV. Finally, a compact freeform surface optical system with a large FOV of 30°×3° is designed on the basis of this initial configuration, which has a focal length of 500 mm and an F-number of 5. The optical system has good imaging quality, no eccentricity or tilt, and easy assembly and alignment, which can provide a reference for the design of the wide-format push-broom imaging space optical cameras.