The Site of Baigongcheng in Cili County has a long history and important archaeological value. A large number of wooden walls were unearthed from the ancient well and a few wooden cultural relics were unearthed from ash pits. This study was carried out in order to comprehend the characteristics and development of the ancient well and materials of daily use in this area, as well as means of wood protection in ancient times. The micro-character of 10 samples from the site was observed by means of optical microscope. It was found that one was Sapindus. mukorossi Gaertn, one, Abies fabri (Mast.) Craib, two were A. acutifolia Hand.-Mazz., two were Toona sinensis A. Juss. and four Machilus pingii Cheng ex Yang. It is preliminarily inferred that the making of well wall was an important work and the wood of well wall was conscientiously used at that time. It also indicates that this area was a mixed coniferous and broad-leaved forest composed mainly of broad-leaved wood that grew in the warm and humid climate in ancient times. The results also provide corresponding information for the protection of wooden relics unearthed in this site.