In order to study the influence of EDXRF beam spot sizes on the analysis of the chemical composition and uniformity of celadon glazes, such as glazes of protoporcelains, Yue celadons and Longquan celadons, samples were tested with two different beam spot sizes2mm and 100μm in diameter. The results indicate that data from the 2mm beam spot size are stable and repeatable; in contrast, data from the 100μm beam spot vary dramatically, and other test methods are required to reduce error as a consequence. Our results show that glazes of proto-porcelains are non-uniform, potentially due to the lack of or imperfect elutriation crawling, cracking, and/or peelingoff. The glaze uniformity of the Yue celadons and Longquan celadons, which are technologically mature, is much better.