Noninvasive detection of temperature with thermography from natural things has been used in many fields and it was attempted to detect the temperature for leaves and branches of trees in the present paper. Leaf and twig temperatures were monitored during the increasing process of temperature under the direct sunshine heating. The difference of specific heat and latent heat from leaves and twigs caused by different water content and transpiration capacity were measured. Not only the leaf temperature, scorch and branch dieback were detected, but the transpiration cooling fail of sweetgum (Liquidambar styraciflua L.) leaves was successfully measured by using thermography. In this study, the local water stress characteristics on sweetgum leaves from specially designed vein severing became special materials for studying the leaf temperature or transpiration failure. The temperature gradient on severed leaf made the thermo image taking easy, with less systematical error. Direct comparison between non-severed lobes and vein-severed lobes on the same leaf lamina makes it more comparable. According to thermography analysis, significant high temperature area was observed and there existed the consistence between high temperature area and the reddened leaf lamina.