Abstract: Fully ceramic micro-encapsulated (FCM) fuel is a type of dispersed particle fuels. Due to the double heterogeneity of dispersed particle fuels, the traditional deterministic method and Monte Carlo method are difficult to be applied to it. In order to overcome this problem, the multi-group effective cross section calculation method for FCM fuel was proposed. To describe the heterogeneity of TRISO particles, the hyperfine group disadvantage factors were calculated by solving a one-dimensional model of the TRISO particle with hyperfine group method in resonance energy range. The matrix and TRISO particles will be homogenized by correcting the hyperfine group cross section with hyperfine group disadvantage factors. Due to the strong self-shielding in thermal energy range, multi-group disadvantage factors were calculated by penetrating probability and collision probability equivalent, and then the matrix and TRISO particles were homogenized by correcting the multi-group cross section with multi-group disadvantage factors. The FCM fuel is able to be calculated as traditional PWR fuel after homogenized. The one-dimensional model of every fuel rod in fuel assembly will be got by Dancoff correction factor equivalent. And then the hyperfine group calculation is carried out based on the one-dimensional rod model to get the effective cross section in resonance energy range. The numerous numerical results show that the proposed method can deal with the double heterogeneity of FCM fuel and get precise effective self-shielding cross section.