Provided are lithium transition metal phosphates where the cation anti-site defects between lithium and transition metals in a lithium transition metal phosphate with a cation well-ordered olivine structure are arranged only in a 1D crystal direction, and a method of preparing the same. The method comprises adding any one selected from the group consisting of an alkali element and an element that has a valence of 5+ or any combination thereof to a solid salt comprising lithium, transition metals, and phosphorus as a starting material to produce a first intermediate material; subjecting the first intermediate to a first heat treatment at a temperature of approximately 250° C. to approximately 400° C. to produce a second amorphous material; and cooling the second intermediate material to room temperature, followed by a second heat treatment at a temperature of approximately 400° C. to approximately 800° C. to produce a final material in which the cation-distribution defect is locally clustered and the distribution has a 1D-oriented arrangement parallel to any one axis direction in the crystal.