The dynamics of droplet has extensive applications and scientific values in natural and industrial fields, and the most typical example is the droplet deformation in shear flow. According to dynamics properties of threedimensional droplet deformation in shear flow, phasefield method is used to make numerical simulation.In order to accurately describe twophase and incompressible flow with surface tension, the modified NavierStokesCahnHilliard equation set is used, and the coupling of Navierstoles equation with CahnHilliard equation is realized by adding surface tension term and concentration convection term into the equation. For numerical solution, Chorin projection method is used to solve NavierStokes equation, and Eyre’s unconditionally stable scheme is used for solving CahnHilliard equation. Numerical simulation results show that the droplet reaches a stable state faster as the Weber number is small and then rotates with the motion of flow field while a larger Weber number makes the droplet keep constantly tensile deformation. Under the same Weber number condition, the droplet shows an obvious twist deformation in a larger Reynolds number. Moreover, the droplet deformation degree is affected by the positions and velocities of up and down boundaries, the closer the distance between the droplet and the boundaries is or the larger the boundary velocities are, the larger the deformation degree of the droplet is.