The dynamic measurement of the diameter of trees was continuously monitored in different parts of Liriodendron chinense by differential electric sensor (3210801,TESA,Switzerland),the response of the meteorological factors was discussed, and the variation rule of tree diameter was analyzed deeply. The results indicated that there were two typical patterns of stem diameter variation (SDV) in different weather conditions,SDV continued expansion on rainy days,while three distinct phases of SDV on sunny days were shrinkage,recovery,expansion,respectively. In general,there were significant differences in diurnal and seasonal variations of SDV. During the measurement,in summer,the contraction of stem diameter started earlier than in winter. The trunk top was maximum about -50-400 mum and the first-order branch was minimum about -120-200 mum. But the amplitude of daily diameter fluctuations was similar in winter,both in -30-30 mum. Stem diameter measurements at the different heights had time lags varying from 0 to 75 min,measurements at the lower heights lagging behind the most obviously. The dominant factors of time lag in different seasons were different. In addition, SDV was strongly associated with the climatic factors,particularly,relative humidity and air temperature,and may lag behind the climatic factors. A model applying multiple regression analysis built with data that included relative humidity,air temperature and vapor pressure deficit explained 84.9% of the variance in SDV. The use of lagged climatic variables increased the proportion of the variance explained (R2 = 0.903) .