According to the morphology of the single-nuclear cell, the eccentric-sphere (ES) model is proposed. The analytic expressions of amplitude function and phase function are revised base on the geometrical-optics approximation (GOA).The intensity distributing and phase distributing of the single-nuclear cell are also simulated by numerical calculation. The incident light orientation and the size of the nuclear on the impact of the backscattering have been discussed. After the analysis, we find that the model and the theory are much closer to the experimental fact compared with the single sphere model. These promote perfecting of the revised theory for inspection of real cell and provide a theory foundation for improving the measuring technique and identification technique of cells.