KTa1-xNbxO3 crystal doped with 0.15% (in mole fraction) Fe was prepared by a top-seeded solution growth method. The dielectric properties, electric-field-induced strain distribution, component distribution and domain structure of Fe: KTN crystal were characterized. The results show that digital holography is a promising method to measure the spatial distribution of strain, and the electric-field-induced strain properties of KTN crystal present a uneven distribution. At room temperature, the maximum strain of crystal is 0.05% when the applied electric field is 435 V/mm, while the strain value is near 0.02% 3/4 area of crystal. There is a relationship among strain distribution, component distribution and domain structure of Fe:KTN crystal. The domain structure of crystal in the region with less Nb content is smaller and the electric-field-induced strain is greater when the room temperature is lower than the Curie temperature.