Tell Abu Yasin is one of the most important sites in Sharkia governorate and dates back to Ptolemaic age. Many tests and analyses were performed to diagnose damage manifestations of some pottery pieces. The research has proved that the clay used in that pottery is Nile Clay, while tempers are sand, grog, and limestone powder, the used shaping technology is potter wheel, surface treatment is slip layer, burning atmosphere inside the kiln was reduced for the first pot and oxidized to the second and third piece. Differential thermal analysis (DTA) indicated that the firing temperature of the first pottery sample was about 705.26 °C; the firing temperature was about 782.99 °C for the second pottery sample and about 773.37 °C for the third pottery sample according to the identified mineral changes. Pottery objects suffer from Physiochemical damage by soil sediments, in addition to phenomenon of fracture, scaling, cracking, weakness, fragility, and crystallization of chlorides, sulfates, carbonates and phosphates salts as a result of burial in saline clay soil. The research recommends that restoration; treatment and maintenance of these pottery pieces should base on results of examinations, analyses and damage assessment that have been proved by the researcher