Abstract: As a new type of fourth-generation reactor, fast neutron reactor is one of the main directions of future nuclear energy development, and the uncertainty of nuclear data has become an important source of uncertainty in the results of its reactor physics calculations. Previous fast reactor uncertainty studies have often ignored the influence of implicit effects. To address this problem, a sensitivity coefficient and uncertainty calculation method that takes implicit effects into account is proposed, and the method is used to analyze the influence of implicit effects on the sensitivity and uncertainty of the k_eff of the sodium-cooled fast reactor ZPR6/7. The results show that: the main diagonal plays a dominant role in the matrix of sensitivity coefficient of few-group cross-section to ultra-fine-group cross-section, and the effect of the implicit effect may be more than 50% for the sensitivity coefficients of certain reaction channels of some nuclides; Implicit effects have a relatively large impact on the uncertainties of ²³Na and ⁵⁶Fe, with the largest impact observed for the radiative capture of ⁵⁶Fe, reaching a relative deviation of −5.6%.