The seepage field around the circular cofferdam is divided into four regions, and the fractional variable method is used to obtain the sequence solution of the water head distribution in the three regions under the cylindrical coordinate system, combined with the continuous conditions between the regions, and the analytical solution of the circular cofferdam steady seepage field is obtained by using the bessel function orthogonality. The correctness and effectiveness of the analytical solution are proved by comparison with the numerical results and the results of other approximate methods. The analytical solution can be used to solve the water inflow of cofferdam and the water pressure of the concrete at the bottom of the cofferdam in the case of double layer soil, and can be degraded to the case of the cofferdam without the bottom of the isotropic soil. Based on the analytical solution, The seepage water pressure distribution law of subsealing concrete is analyzed, and the instability failure law of subsealing concrete considering seepage influence is discussed with an engineering example. The results show that the water pressure on the concrete under seepage is not uniformly distributed, but in the form of small in the center and large in the periphery. The permeability coefficient and thickness of the concrete at the bottom of the seal significantly affect the magnitude and distribution of the seepage water pressure.