The shaft-hub coupling is a basic component used in power transmission.Due to the unique structure and working principle of the hydraulic expansion tight coupling(also known as hydraulic expansion sets),it has the functions of fast installation and overload protection.Use of the no momental theory and the momental theory of thin cylinder,the relationship between coupling cavity pressure and amount of ring mezzanine deformation was deduced.Through experimental tests,the correctness of the theoretical formula was verified,then the causes of relative error were analyzed.