After burial for over two thousand years, the lacquered paint layer on the surfaces of polychrome potteries of Qin Terracotta Warriors and Horses always curve and peel off. The problem of reattaching these paint layers has been a focus as well as a challenge for art conservators. Based on observations from previous work done at the Mausoleum Site Museum on the subject, several key parameters that may affect the reattachment process were noted. These parameters include pottery body water content, PEG200 uptake rate, soluble salts content, clay attachment rate, painted layer water and PED content and temporary reattachment reagent composition. It is found that optimal reattachment results were obtaiined when 1) the pottery water content is below 5% and there was little PEG200 solution penetration; 2) the pottery itself is desalinated; 3) microlevel filler is mixed with the glue; 4) PEG200 content is gradually increased during the process; 5) the contemporary attachment agent is removed. All these treatments help the reattachment process, increase the attachment strength and protect against aging. This research provides information regarding insitu conservation of polychrome relics.