It is known that single-core REBCO-coated conductors has a large screening current induced magnetic field, therefore, a large AC-loss due to the magnetic hysteresis is generated in coils. Recently, we developed multi-core REBCO sprit wires with three methods, as V-bending, pressure concentration, and tearing. In results, magnetization was decreased above 70%, with reducing of area in hysteresis. This indicates that the AC-losses in REBCO-sprit wires were improved largely. Based on these results, we investigated the AC-loss in coil with magnetic field simulation of the coil. For the magnetic field simulation, the maximum magnetic field of each split wire in AC-circuit along vertical direction of tape surface was calculated by using FEM. And then, each AC-loss of turn in coil is obtained by using the magnetization measurement results. Finally, the AC-loss of entire coil was simulated and evaluated. As an example for magnetic field simulation, Fig. 1 shows the results of a maximum magnetic field distribution in a coil. The cross-sections of all sprit wires in a half of coil are shown by a square frame. This model of coil was calculated with an inner diameter of 80 mm, an outer diameter of 111 mm, and 61 turns. The peak current in AC-circuit is 30 A.