Abstract: The nonlinear thermal instabilitv in an idealizeddvnamical svstem ofdeuterium-tritium fusion plasma is discussed in the present paper.There are mass andenergy exchanges between the system and its surroundings.The evolution equations ofzero-dimension approximation are adopted.Firstly,the nonlinear thermal stability criteriaare obtained for the autonomous svstem and five different confinement laws.Then,thenonlinear evolution equations for the disturbances of unstable solution are solveJd for theconstant conf...