The paper carried out direct slow shear test and unconfined compressive strength test for reinforced Shanghai clay with polyvinyl alcohol fiber under different conditions in order to study the effect of polyvinyl alcohol fiber on Shanghai clay shear and compressive strength,and the mechanism of polyvinyl alcohol fiber reinforced materials on the strength of Shanghai clay. The results show that after incorporating polyvinyl alcohol fiber in Shanghai clay, the shear strength and compressive strength are improved compared with the pure soil, which increase by 73.7% and 49.5% respectively;the optimul reinforcement rates of shear strength and compressive strength are 1.0% and 0.8% respectively,while the anti-deformation ability is improved compared with pure soil;in direct slow shear test, when the vertical load is 50kPa, the stress-strain curve possesses strain softening; when the vertical load is 100, 150 and 200kPa, the stress-strain curve is strain hardening;in the direct shear tests, the influence of Shanghai clay incorporated by polyvinyl alcohol fiber on cohesion is larger and that has almost no effect on internal friction angle.