After the development of industrialization and rapid economic growth, people began to avoid environmental problems and pursued convenience and comfort. However, the pace of industrialization and environmental deterioration was proportional, and now, as industrialization develops further, environmental problems are becoming more and more tangible to people. Although internal combustion locomotives have been produced and operated for over 100 years, in line with the carbon regulation schedule stipulated due to extreme automobile exhaust, new vehicles will be gradually released from 2025 as hydrogen and battery vehicles, From 2030 onwards, it is expected that the era of automobile transformation will come when only eco-friendly vehicles such as electric vehicles and hydrogen vehicles will be released. In addition, refrigerants used in air conditioners and refrigerators are considered to be hundreds of times more powerful than carbon dioxide and 10,000 times more powerful than carbon dioxide. In October 2016, a total of 18 HFC refrigerants were designated for regulation through the Kigali Amendment Protocol. Korea, classified as A5 country group 1 in the Kigali Amendment Protocol, will stop producing HFC-based refrigerants as of 2024, reduce it by 10% in 2029, and reduce it by 30% in 2035, aiming to reduce 80% by 2045 is doing with However, there are still many HFC refrigerants used in many refrigeration fields such as air conditioners and vehicle refrigerators. Therefore, this paper is an analysis experiment on the characteristics of condensation heat transfer and pressure drop of R-1234yf in a 6mm inner diameter double tube heat exchanger to which an HFO-based refrigerant designed to replace the HFC-based refrigerant that is depleting the ozone layer and promoting global warming due to its high GWP. Experimental conditions were changed to a mass flux of 100, 200, 300 kg/m2·s, a saturation temperature of 40, 50℃, a cooling water temperature of 25, 30, 35℃, and a vapor quality of 0-1. The experimental results are as follows. The condensation heat transfer coefficient and pressure drop increased with increasing mass flow rate and increased with increasing vapour quality. The higher the saturation temperature, the lower the condensation heat transfer coefficient and pressure drop. In addition, it can be seen that the heat transfer coefficient increases as the cooling water temperature decreases. Based on these results, it can be concluded that the increase trend of the heat transfer coefficient and pressure drop is proportional. It is considered that the research results of this paper can be used as the basis of design data for the condensing heat transfer and pressure drop of the heat exchanger using R-1234yf.