The environmental problem caused by refrigerant has become the focus all over the world.As the most typical natural refrigerant,CO2,of course,becomes the research focus.This paper introduces the development and application status of CO2 refrigeration and heat pump technology.The researches on CO2 refrigeration and heat pump,carried out by Thermal Energy Research Institute,Tianjin University,also are presented in this paper. The environmental problem caused by refrigerant has become the focus all over the world. As the most typical natural refrigerant, CO2, of course, becomes the research focus. This paper introduces the development and application status of CO2 refrigeration and heat pump technology. on CO2 refrigeration and heat pump, carried out by Thermal Energy Research Institute, Tianjin University, also presented in this paper.