Swelling is the typical characteristic of weak swelling soil,and is the most important cause of the damage of swelling soil structures.It is of great importance to estimate the deformation of swelling soil in some specific conditions,and it is not only important but also necessary to establish the calculation model for weak swelling soil. In view of this, on the basis of analyzing the influence factors of linear swelling ratio,we carried out swelling deformation tests on weak swelling soil of the slope of Xuhe river in different initial status.We also studied the influences of humidification ratio,degree of compaction and overburden pressure on the linear swelling ratio,and established the calculation model for linear swelling ratio in consideration of humidification ratio,degree of compaction and overburden pressure.Finally we used the test data of other scholars to verify the calculation model,and the verification results showed that the calculation model could well fit the swelling deformation of compacted weak swelling soil.