Aramid fiber-reinforced plastic (AFRP) has been applied in severe environmental conditions, such as aeronautical and space environments, etc. AFRP rod has been particularly developed as a structural material that has the advantages of light weight and high strength. Therefore, it is necessary to examine its strength in various environments. In this study, tensile tests were carried out to measure the tensile properties of AFRP rod on the marketfor reinforcement of concrete at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4.2 K). Especially at cryogenic temperatures, it is difficult to perform a tensile test of the bar because the specimen slips through the jig grip. To prevent the AFRP rod from slipping, tensile tests were carried out with some filling conditions. The applicable and appropriate tensile test conditions were established by modifying the jig grip, treating the surface of the rod and using cryogenic epoxy infill to grip the AFRP rod. Additionally, the effects of cryogenic temperatures on the tensile properties were evaluated. From the tensile tests, the tensile strength decreased about 7% at 77 K and about 15% at 4.2 K as compared to room temperature. However, they were more than 1100 MPa. Additionally, the AFRP rod included a temperature dependence in which the Young's modulus increased as the test temperature decreased. The increased was approximately 60% at 77 K and 4.2 K as compared to the room temperature measurement. From the results of dynamic viscoelastic measurement, it was confirmed that the Young's modulus increased because aramid fiber was more dominant than epoxy.