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 proto - porcelains, Yue celadons and Longquan celadons, samples were tested with two different beam spot sizes - 2 mm and 100 [micro]m in diameter. The results indicate that data from the 2 - mm beam spot size are stable and repeatable; in contrast, data from the 100 [micro}m 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 peeling - off. The glaze uniformity of the Yue celadons and Longquan celadons, which are technologically mature, is much better.