Purpose <p>In existing mathematical models, the component behavioral intervention in multi-body systems and offset installation of gears constrained by spatial environment are seldom concerned, which significantly hinders the upgrade design and intensive comprehension of gearbox.</p> Methods <p>Depending on the rotor modeling method, bearing model considering the time-varying misalignment factor and gear mesh analysis technology, the analysis method for bearing–rotor–gear coupling system with asymmetric installation is constructed.</p> Results <p>The bending deformation of the flexible rotor is induced by the combined effects of meshing forces and bearing forces, and rotor deformation is alleviated by the eccentric installation of gears, causing the inflection point of the deformed curve to shift toward the gear offset direction. The bearing contact angle is triggered due to the rotor deformation, leading to a cascade of variations in contacting stiffness and clearance, while the contact angle is attenuated by the eccentric installation of gears, and the distribution coefficient of bearing forces maintains a linear correlation with the gear offset distance. Moreover, the gear misalignment angle is markedly amplified by the asymmetric mounting form, resulting in an eccentric load distribution characterized by contact stress and line load concentrated on one flank of the tooth surface. The mesh force and system vibration intensity could be weakened by a moderate amount of gear eccentricity, whereas reverse static transmission errors would be introduced by excessive offset distance. </p> Conclusions <p>The study reveals the intrinsic operating mechanisms within the gearbox, as well as the influence of gear offset installation on the system kinetic behavior and vibration responses.</p>