Recently,climate change and biological acclimation to it have become one of the most popular research focuses.This article clarifies the concepts of acclimation and phenotypic plasticity,and then summarizes the related theoretical questions.It is concluded that the concepts of acclimation and phenotypic plasticity should be generalized,and attention should be paid to the differences in them.At last,four theoretical issues relating to acclimation were further discussed:1) capability of acclimation and phenotypic plasticity should be discussed separately in stressful or non-stressful environments;2) cost-benefit analysis is key to understand capability of acclimation and plasticity;3) the response model indicators are important to justify whether acclimation is adaptive;and 4) phenotypic optimization is a developmental direction for modeling of acclimation in the future.