In order to reveal the decarboxylation transformation mechanism of cannabidiolic acid (CBDA) in Cannabis sativa L.,the basic thermodynamic parameters in the transformation process were obtained by the group contribution method and Watson formula.Then,the reaction Gibbs free energy,reaction equilibrium constant and equilibrium conversion rate were calculated according to the classical thermodynamic formula from 40 ℃ to 140 ℃.The effects of temperature and water content in C. sativa flowers and leaves on the decarboxylation of CBDA were analyzed by thermal decarboxylation conversion experiment.The thermal decarboxylation conversion mechanism function model and conversion activation energy of CBDA were determined according to the conversion rate of CBD.The results showed that the thermal decarboxylation of CBDA could occur spontaneously from 40 ℃ to 140 ℃,and the spontaneous trend increased with the increase of temperature.In the process of thermal decarboxylation,the increase of CBD conversion rate was positively correlated with temperature and water content of flowers and leaves.By fitting with the kinetic function model,the most probable model of CBDA decarboxylation conversion in C. sativa flowers and leaves conforms to the F₁ model.The activation energy of the reaction conversion calculated is 83.77 kJ/mol by this model.In summary,CBDA in C. sativa can be automatically decarboxylated to CBD from 40 ℃ to 140 ℃.The results provide theoretical and experimental support for the selection of high content CBD conditions for C. sativa industrial processing.