This paper shows results of a design work of a program that is to develop a large power single phase high temperature superconducting (HTS) transformer. The program forms a part of a national project in Korea. A target of the design work is an HTS power transformer with rated voltages of 154 kV/22.9 kV and material for windings is supposed to be coated conductor. The design results presents in this paper will include: 1)HTS winding structures for high voltage in liquid nitrogen, 2)design result of continuously transposed coated conductor (CTCC), 3)conceptual design of high voltage bushings, 4)cooling system. A feasibility study will succeed to this design work for construction of a prototype HTS power transformer with capacity/voltage of 33 MVA/154 kV.