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In light of environmental issues, the lead-free ferroelectric single crystal K(Ta1–xNbx)O3(KTN) has attracted considerable interest due to its excellent piezoelectric properties. This research focus on improving the piezoelectric performance of KTN by engineering domains through polarization in the [011]cdirection. The full–matrix parameters of KTN crystals after polarization along the [011] direction were determined. The finding reveal that KTN polarized in the nonspontaneous polarization direction [011]cexhibits higher piezoelectric constants (d33= 156 pC/N, d15= 155 pC/N) and dielectric constants (ε33T∼ 2337). Additionally, tensor matrix transformation techniques were utilized to analyze the directional dependence of the piezoelectric (d33*), dielectric (ε33T*), elastic (s33E*) constants, and electromechanical coupling coefficient (k33*). The results indicate that these constants reach their maximum values along the polarized [011]cdirection. A comparison of the experimental polarization values in the [011]cdirection with those calculated for a single-domain state, demonstrates that ferroelectric domains in KTN crystals contribute significantly to the piezoelectric properties. Finally, polarized light microscopy was used to conduct a detailed analysis of the domain structure in KTN single crystals, revealing various orientations and sizes of domain walls. This research offers strategies for optimizing piezoelectric performance.