Abstract: Burnup limit is important for the safe use and design improvement of fuel rod. Burnup limit of FA300 fuel rod was not studied before. Uncertainty and sensitivity analysis was the basis of burnup limit research. Current methods such as bounding method, Monte Carlo method, etc. are hard to represent the information of uncertainty and sensitivity in analyzing fuel rod characteristics. With ANN (artificial neural network) based response surface method, mathematic model was reconstructed in explicit form. Then uncertainty information was obtained by sampling on the response surface. As to some special form of ANN model, sensitivity information was obtained with simple algebraic calculation. The results show that corrosion and strain of the cladding are the most limiting criteria for FA300 fuel rod. Compared to the post irradiation examination data of lead assembly irradiated in Qinshan Phase-Ⅰ NPP and other related experience, burnup limit of FA300 fuel rod is 55 000 MW•d/tU.