Thermoelectric devices based on thermoelectric effect have special advantages in the conversion between heat and electric energy, and the performance optimization of thermoelectric device has the practical significance, Based on the finite-time thermodynamic theory, this paper studies the thermodynamic characteristics of thermoelectric generators and refrigerators by using the ecological criterion, On the basis of constructing the ecological criterion function,the expressions of efficiency and coefficient of performance (COP) of thermoelectric devices are derived, and the influence of ambient temperature and thermoelectric figure of merit on efficiency and COP is explained. It is found that when the ambient temperature is low (high).which is helpful for enhancing the efficiency (COP) of generators (refrigerators). In addition,the relationship between ecological criterion and trade-off optimization criterion is definitely clarified.