A fined 3D calculation model of longitudinal joints of large crosssection rectangular shield tunnel with embedded parts is established by finite element software ABAQUS based on fullscale mechanical testing results, so as to analyze and estimate the rationality of the segment joint structure and stressing. The working states of every joint under normal operating conditions are estimated qualitatively and quantitatively; and then the stressing characteristics of joint under positive and negative bending moment are studied. The results show that: 1) The bending momentrotation angle curve of the segment presents a threefold line mode under positive bending moment. The joints are in the second stage under normal operating condition, where the rotational stiffness is about 100 MN·m/rad; the components are all in elastic condition and the design and location of the joints are rational. 2) The bending momentrotation angle curve of the segment presents a doublefold line mode under negative bending moment. The joints are all in the first stage under normal operating condition, where the rotational stiffness is about 276 MN·m/rad. However, the negative bending moment is quite large and the safety stiffness is low, which should be paid more attentions to in design.