XRD technique was employed to examine Sm-modified PbTiO3 piezoelectric ceramics with typical ultra-high electromechanical anisotropy. By introducing crystal plane orientation density ρ(hkl) and establishing wall translation model for 90°ferroelectric domain switching, a quantitative analysis and discussion on the domain texture change within the ceramic disks poled at various electric forces has been carried out. The results indicate that 90°domain walls in the modified PbTiO3 ceramics show a strong spatial orientation preference, and little changes in their orientation can result from poling treatment but noticeable wall displacement appears. Another noteworthy result is that the thickness electromechanical coupling coefficient Kt develops with poling field almost at the same pace as the orientation density gain △ρ(002) of the crystal plane (002).