In this paper, mechanical characteristics of sandstone under hydraulic fracturing were investigated by uniaxial compression tests (using RLW-2000M Coal and Rock Computer Controlled Rheological Testing Machine). Transformation laws of strain-pore water pressure curves are the research highlights. The mechanical characters of sandstone under hydraulic fracturing were discussed based on pore water pressure, rock strain and water volume. In addition, we assessed the hydraulic fracture morphology and failure type of sandstone. The results show that the typical deformation evolution involoves four stages in hydraulic fracturing process, and well the characteristics of the pore fissure water injection stage, the elastic deformation stage, the volume expansion stage, and the gloable rupture stage are revealed. The power of negative exponential can fit the ε₁-t and the P-V_p curves. Tensile deformation and shear deformation interact with each other during the crack initiation and propagation process.