This paper considers the influence of internal heat exchanger and capillary tube on the efficiency of small refrigeration system using eco-friendly refrigerants such as R290, R600a, R1270, and R717. A refrigeration system using such internal heat exchanger and capillary tube may improve performance, but may degrade performance. Therefore, this paper used a mathematical model in a normal state to understand performance characteristics as to what change occurs when internal heat exchanger and capillary tube are attached to eco-friendly refrigerant based on R134a. In addition, the effects of operating conditions such as refrigerant flow rate, evaporation temperature, condensation temperature, subcooling degree internal heat exchanger length and capillary tube length were analyzed. The result showed that the evaporation temperature, condensation temperature, subcooling degree, internal heat exchanger length and capillary tube length had an effect on the refrigeration capacity and compression power. Therefore, it is necessary to design a refrigeration cycle using an eco-friendly refrigerant by grasping these effects in detail.