An optical model of Chebyshev-shaped particle with ellipsoidal nucleus is established for agranulocyte, aiming at their morphological changes due to the disturbance of extracellular fluid. Based on the T-matrix method, the scattering characteristics of linear polarization of the white blood cells (WBCs) at different morphometric parameters and nucleus to radius ratios are numerically simulated for linearly polarized incident light. The scattering polarization characteristics are compared with those of WBCs without the disturbance of extracellular fluid. The research results show that the degree of linear polarization of the scattered light is more sensitive to the external liquid disturbance at the side-scattering region than that at the backscattering region, the stronger the external fluid disturbance, the greater the influence on light polarization. Moreover, the larger the nuclear deformation parameter, the greater the influence of extracellular fluid on the polarization of scattered light.