Stress analysis of split ring with four different radius ratios under the compressive load is made by the photoelastic experiment and the numerical analysis through the FEM. The results of the two methods agreed well. Above results are also compared with those of the theoretical formula in order to confirm the range in which the formula of the curved bar is applied in connection with the radius ratio. The results of the two methods agreed well with those of the formula for the radius ratio, 3/2 and 9/7 within small errors of around 7% and 5% respectively.