Comprehensively considering the various thermoelectric effects including the Thomson effect， a computational model of a series two-stage thermoelectric cooler that works in adiabatic surface space and non-adiabatic surface space is established. The effects of transient changes of parameters such as cold and hot junction temperature， and interstage temperature difference on the performance of a two-stage thermoelectric cooler are analyzed. The variation law of performance parameters such as cooling capacity， cooling space temperature and coefficient of performance with time is obtained. When the input current， the number of thermoelectric couples and the distribution ratio of thermoelectric couples are changed， respectively， the minimum cooling temperature， the time-consuming to reach the stable temperature， the refrigerating output and the change of the cooling coefficient of the two models are compared. The results show that， compared with single-stage refrigerators under the same conditions， two-stage refrigerators take longer to cool down but can achieve lower cooling temperatures. Appropriately increasing the current can effectively reduce the cooling time. There exists the optimal current， the number of thermoelectric couples and the distribution ratio of thermoelectric couples， which make the temperature of the cooling space the lowest and the coefficient of performance of the cooler to be the largest， respectively.