Abstract The article presents the test results of the relaxation modulus of SMA. The samples of SMA mixture were made using polymer modified bitumen PMB 45 / 80-55 (PMB-N) and highly polymer modified bitumen PMB 45 / 80-80 (PMB-HM). Determination of the relaxation modulus were made using DT-CY test (direct tensile test) at 10 °C, 20 °C and 40 °C. To describe the relaxation phenomenon of the bituminous mixture a logit model has been used. The test results indicates that the use of the highly modified bitumen (PMB-HM) caused the increase in the stiffness modulus SMA at high temperature / low frequencies. As a result, the presence of highly polymer modified bitumen will increase the resistance to the permanent deformation of SMA.