<p>The soil in the sloping ground is subjected to static shear stress and multidirectional cyclic shearing simultaneously in the course of an earthquake, which significantly affects its cyclic behavior and liquefaction resistance. To investigate the effect of static shear stress and loading paths on the undrained cyclic behavior of saturated medium-dense sand, a series of undrained unidirectional and multidirectional cyclic simple shear tests were conducted under unidirectional, circular, oval, and 8-like loading paths, with static shear stress ratios ranging from 0.00 to 0.20. The results indicate that the presence of static shear stress is detrimental to the liquefaction resistance of medium-dense sand under both unidirectional and multidirectional cyclic loadings. Specimens subjected to an 8-like loading path are more prone to failure compared to those under oval and circular loading paths. Furthermore, when considering the effect of static shear stress, the liquefaction resistance of medium-dense sand under multidirectional cyclic loading is reduced to 43–79% of that under unidirectional cyclic loading. A unique relationship between normalized pore pressure ratio and cumulative dissipated energy per unit volume is not affected by static shear stress. An improved pore pressure prediction model, which incorporates the effect of static shear stress under multidirectional cyclic loading, is proposed.</p>