Calderon's method was introduced to electrical capacitance tomography in this paper. It is a direct algorithm of the image reconstruction for low-contrast dielectrics, as no matrix inversion or iterative process is needed. It was implemented through numerical integration. Since the Gauss–Legendre quadrature was applied and can be predetermined, the image reconstruction process was fast and resulted in images of high quality. Simulations were carried out to study the effect of different dielectric contrasts and different electrode numbers. Both simulated and experimental results validated the feasibility and effectiveness of Calderon's method in electrical capacitance tomography for low-contrast dielectrics.