Abstract: In the design phase of China Experimental Fast Reactor (CEFR), the uncertainty analysis was mainly based on the zero-power simulation experiment in Russia. There are some shortages in the work of nuclear design uncertainty analysis and evaluation. In this paper, based on statistical sampling method, deterministic theory perturbation method and direct perturbation method, different sources of uncertainty were evaluated. The uncertainty of main nuclear calculation results such as k_eff, control rod worth, sodium void effect and power distribution was given. Through the analysis work of CEFR, a method framework for the evaluation of uncertainty was established. The framework and method lay the foundation for the uncertainty analysis of nuclear design for China Demonstration Fast Reactor.