The Calcium modified PbTiO3 ceramics with large piezoelectric anisotropy was poled in consecutive steps. X-ray diffraction (XRD) found that the values of inter-planar spacing, d002 and d200, increased with poling field at initial poling stages. A noticeable drop of the d¬002 and d200 at the coercive field was observed. The residual stresses measured by the angle tilt method were introduced. The relations of d002-sin2ψ and d¬¬200-sin2ψ at different poling stages were simulated by a mathematic model. The linear terms in the model are related to the macro-stress which may cause an elastic deformation; the exponential term in the model is related to the micro-stress which may cause a plastic deformation by the 90o domain switch. The results show that macro-stress and micro-stress decreased and the decay speed along angle increased as to the d002 lattice spacing. The residual stresses related to the d200 lattice spacing were almost not changed.