Ultra-depth field microscopy, X-ray fluorescence, X-ray diffraction, and gas chromatography-mass spectrometry were used to analyze the materials used to make the colored drawings in the Bell Tower in Xi’an. These studies show that the technique of“only plaster layer”is the colored drawing’s background plaster. Red pigments were hematite and the green pigment was an artificial pigment (emerald green); the binding medium was composed mainly of animal glue. This research is of significance for restoration and conservation of colored paintings of the Bell Tower in Xi’an.