The divergence problemof tree radial growth-climate relationship arose in the 1990s. Initially,tree-ring researchers found the phenomenon that the temperature sensitivity of tree's radial growth decreased at Alaska's alpine timberline. Then,similar reports appeared in many regions of the mid- and high latitudes in the northern hemisphere. This discovery raises a challenge to the established basic hypothesis in dendrochronology-uniformity principleof relationship of radial growth-climate,and to the scientificity of data derived from ring index based on the hypothesis. Despite extensive research published,there are lots of arguments about the causes and mechanisms of the formation ofdivergence problem. To clarify the formation mechanism ofdivergence problem,this review sorted the related research in the literature into location,tree species,driving factors and analyzed the misjudgment induced by research methods. The results showed that the tree species involved indivergence problemare growing mainly in the regions of mid-high latitude and high altitude,and sensitive to moisture and temperature. The climate warming and drying in these regions resulted in soil water deficit(exceeding the water threshold) or temperature-induced physiological changes of trees(exceeding the temperature threshold of normal growth or dormancy) . Consequently,climate sensitivity or tree growth decreased. There are some other explanations for the formation mechanism,including the change of atmospheric CO_2 concentration,the influence of anthropogenic activities;however,the threshold hypothesis is the most possible explanation for the formation mechanism ofdivergence problem.