Abstract: Using lemon juice as raw material, the thermal degradation kinetics of vitamin C was studied by changing temperature.On the basis of that, the research of protective effect of erythritol which was added in the lemon juice on vitamin C was carried out through some kinetic parameters such as reaction rate constant and activation energy.The results showed that vitamin C in the lemon juice was unstable with heat treatment in the process of storage, its degradation obeyed first order reaction kinetic model.ln this experiment, 1%³%adding concentrations of erythritol could slow down the degradation rate of vitamin C.When its concentration was 2%, the degradation reaction activation energy of vitamin C reached the most (75.47kJ/mol) .which was 9.79kJ/mol higher than that of control.Therefore, to some extent, erythritol could protect vitamin C from degrading.