A new method of fabricating HTS coils was proposed with excellent performance for the critical current and magnetization loss properties. In the winding process of the coil, continuous control of twist angles around tape axes is adopted to reduce the degradation of these properties due to flat-on oriented magnetic fields applied to the wound tape. The effect of this method on improvement of the current capacity of tapes was estimated theoretically for a large scale Bi-2223 magnet. The expected capacity at 77K, 66K and 20K becomes 1.80 times, 1.70 times and 1.46 times as large as that for the previous coil winding, respectively. This result shows that compared to the old coil, and under identical operating currents, the new type coil would allow a great reduction in the amount of Bi-2223 tapes needed. Another effect of this method on the magnetization loss is also estimated by using the data observed for short tapes; one order reduction of loss can be expected.