The joint bending test was carried out to study the bending mechanical property and deformation characteristics of the F-type socket joint in rectangular pipe jacking tunnels under the conditions of foundation settlement, construction disturbance and different upper loads. The supporting function of soils under different geological conditions on the rectangular pipe jacking was simulated by arranging different numbers of equivalent foundation springs at the bottom of the pipe. The test results show that the greater the foundation stiffness is, the greater the joint bending moment will be at the same loading displacement, which leads to greater joint opening deformation. When the pipe joint itself produces large deformation, the change rate of joint opening slows down, and the slope of the bending stiffness curve of the joint increases. The bending bearing capacity of the joint is closely related to the foundation stiffness. The greater the foundation stiffness is, the higher the bending bearing capacity.