Abstract: The distribution of guaiacyl lignins of Chinese fir in Xichou and Yiliang,Yunnan Province,China,was observed with UV microspectrophotometer(Carl ZeissUMSP 80).The results were as follows:1.Tracheid secondary walls of Chinese fir in theabove two Chinese fir-producing areas had a peak at 560 nm.2.The consistency ofguaiacyl lignins in tracheid secondary wall of Chinese fir in Xichou was lower than that inYiliang but the consistence of guaiacyl lignins in tracheid intercellular layer in Yiliang waslower than that in Xichou.3.The distribution of guaiacyl lignins in tracheid secondarywalls differs between early wood and late wood of Chinese fir in Xichou and Yiliang. Thepeak of guaiacyl lignins in tracheid secondary walls of Chinese fir in Xichou was graduallydropped from early wood to late wood ofan annual ring. It followed a changing pattern ofnormal timber.The peak of guaiacyl lignins in tracheid secondary walls of Chinese fir inYiliang was found undulated with waves of change which showed abnormal instructure.4.There were differences in concentration of guaiacyl lignins in tracheid secon-dary walls of Chinese fir in the two areas effecting main mechanic strength of timber.Withthe decrease of concentration of guaiacyl lignins in tracheid secondary walls,main me-chanic strength of wood increased,conversely,it decreased.