Only few published information are available in the conservation literature on materials and techniques used by ancient Chinese artists to decorate wooden architectural buildings. This paper presents the results of a joint research aimed at collecting technical information through an historical survey and studying the results of the scientific examinations carried out on the paint samples collected from the decorated surfaces of the Drum Tower in Xi'an, a Ming Dynasty monument built up in 1380 A.C. Optical microscopy of the cross-sections, scanning electron microcopy coupled with energy-dispersive X-ray analysis (SEM-EDX), X-ray diffraction as well as pyrolysis gas chromatography mass spectrometry have been used to characterize both the inorganic pigments composition and the binding media used. The analytical results showed that the materials composition and technique used to plaster the wooden surface are in good agreement with the information gathered through the historical survey. In fact, clay, lime, siccative oil, probably tung oil and fabrics strips are the main plaster components. At the same time the plaster represents the priming material for the painted decorations, whose pigments composition indicates that they are both original and applied on the occasion of a past restoration procedure carried out in the 18 century even though the binding medium used follows the ancient tradition. -- MCI