In order to explore the enhancement effect of palm fiber on the mechanical property of quartz sand, the reduced triaxial extension test was carried out to test the shear property of palm fiber reinforced quartz sand under saturated condition. The stress-strain curves, initial elastic modulus and secant modulus of saturated quartz sand reinforced with different fiber lengths and contents were calculated. The varying law of the shear strength of palm fiber reinforced quartz sand with the fiber content was analyzed based on the Mohr-Coulomb criterion. Furthermore, the strengthening effect of palm fiber on the mechanical properties of quartz sand was obtained through comparing the volume strain and porosity of contrast plain sand and reinforced sand during shear process. The results show as followed. Palm fibers can enhance the stress-strain strength of quartz sand during tensile failure, while the optimal fiber content and length for improving the peak stress and residual stress of quartz sand are 0.9% and 12 mm. The initial elastic modulus and peak secant modulus of palm fiber reinforced quartz sand increase with the rise of effective confining pressure, and the overall stiffness is positively correlated with the effective confining pressure. The strengthening effect of palm fibers on the shear strength of quartz sand only appears in the low confining pressure state. The critical porosity and shear dilating of quartz sand are reduced by the addition of palm fibers. The research results are helpful to promote the applications of palm fiber reinforced sand and provide the corresponding theoretical basis.