In consideration of the mechanism for shear-stress-induced Ca²⁺ influx via ATP(adenosine triphosphate)-gated ion channel P2X₄ in vascular endothelial cells, a modified model is proposed to describe the shear-stress-induced Ca²⁺ influx. It is affected both by the Ca²⁺ gradient across the cell membrane and extracellular ATP concentration on the cell surface. Meanwhile, a new static ATP release model is constructed by using published experimental data. Combining the modified intracellular calcium dynamics model with the new ATP release model, we establish a nonlinear Ca²⁺ dynamic system in vascular endothelial cells. The ATP-mediated calcium response in vascular endothelial cells subjected to shear stresses is analyzed by solving the governing equations of the integrated dynamic system. Numerical results show that the shear-stress-induced calcium response predicted by the proposed model is more consistent with the experimental observations than that predicted by existing models.