Abstract: In order to investigate the transverse grain deformation of elm square timber during drying, Digital Image Correlation technology（DIC） was used to monitor the full-field strain distribution of the transverse grain at different temperatures in real time and with 50 mm thick elm square timer as the object. The law and difference of radial strain at different temperatures were analyzed, and the relationship between water content distribution, strain law and cracking was explored. The results showed that the transverse strain distribution of elm square timber was small in the middle and large in the edge at three different temperatures. The maximum chord and radial strains at 40 ℃ were 0.036 6 and 0.033 6. At 60 ℃, 0.045 2 and 0.042 3; at 80 ℃,those were 0.059 8 and 0.051 1. With the decrease of water content, the chord strain and radial strain gradually increased, and crossover occured when the water content was about 30%（60 ℃） and 40%（80 ℃）, respectively, and the strain direction changed. The uneven distribution of water content led to the difference of strain distribution. The cracking occurred after the moment of maximum strain difference, and the cracking occurred when the water content was about 15% and 30%, respectively. Temperature had significant effects on moisture and strain distribution of elm square timber（P＜0.05）.