Abstract: A typical Qinshan Phase-Ⅱ PWR plant was selected as the base case for methodology study of thermal-hydraulic analysis for the best array of annular fuel assembly applied in the PWR core. A range of arrays from 11×11 to 15×15 for different sizes was investigated by using a sub-channel analyzer named SAAF. On the consideration of minimum departure from nucleate boiling ratios, pressure drops and fuel temperatures, the most promising option was found to be the 13×13 array of annular fuel assembly. The calculation results in this paper provide initial calculation model for correlative analysis.