Abstract: Bearing capacity of buried flexible pipes depends closely on the support provided by surrounding soils, and the interaction forces between the pipe and the soil are crucial for ensuring a stable operation of pipeline. When differential ground deformations occur, flexible pipes are susceptible to angular damage at the joints due to uneven support. This paper investigates the mechanical behavior of flexible pipe joints under differential ground deformations through laboratory model test. Using the Winkler elastic foundation beam theory, theoretical formulas are proposed for calculating the rotational angle of flexible pipe joint under conditions of fully released moment, partially transmitted moment and fully transmitted moment. These proposed formulas are analyzed and verified using model test data. The research reveals that the deformation of flexible pipe joint is closely linked to the amount of differential ground deformations. Compared to the formula for fully released moment joints, using the formula for partially transmitted moment joints gives a more accurate calculation of the rotational angle of the pipe joint under differential ground deformations. As the pipe diameter, burial depth and internal friction angle of the backfill material increase, the maximum allowable differential ground deformations that the pipe joint decreases accordingly. Additionally, the joint rotational angle shows trends of linear, logarithmic, and exponential growth, respectively. Furthermore, with the increase in differential ground motion, these growth trends become increasingly significant.