Abstract: Welded hollow spherical joints are often subjected to axial forces and bending moments, which are prone to fracture and lead to progressive collapse of the whole structure. To improve the collapse resistance of traditional welded hollow spherical joints, inner sleeves are added at the connections between the members and hollow spherical. Static experiments were conducted on welded hollow spherical joints strengthened by inner sleeves. The accuracy of the finite element models was verified by comparing numerical and experimental results. The effects of different geometrical parameters of the inner sleeves were further investigated and the design suggestions of the inner sleeves were put forward. Based on the component method model, proposed was a practical calculation method for the bending stiffness and equivalent sectional moment of inertia of the reinforced areas. Additionally, the welded hollow spherical joints strengthened by inner sleeves and slider (WHSJ-ISS) and strengthened by outer sleeves (WHSJ-OS) were analyzed respectively. The results show that the inner sleeves change the bending stiffness of the joint, which can significantly improve the bearing capacity and deformation capacity of traditional welded hollow spherical joints. However, when the bending stiffness reaches a certain level, the rotational capacity of the joint will be reduced significantly, which is not conducive to the exertion of the catenary mechanism. WHSJ-ISS and WHSJ-OS can also improve the collapse resistance of traditional welded hollow spherical joints, and the second fracture of the WHSJ-ISS provides an additional resistance reserve for structures.