Abstract: In winter road pavements are frequently covered by ice and snow because of the low temperature. Deicing salt is one way to deal with the icing coverage and clean the pavements. The SEM and bending beam rheometer (BBR) were used to study microstructure and rheological properties at low temperature of three kinds of asphalts (matrix asphalt, SBS(polystyrene-polybutadiene-polystyrene) modified asphalt and rubber powder modified asphalt) before and after the salt freezing cycle. The results show that the modified agent exists in asphalt with specific structure, and the two have good compatibility, which can adsorb asphalt better, so that the low temperature elasticity or viscosity of asphalt has been increased and then the low temperature performance of asphalt can been improved. After salt freezing cycle, the structure of asphalt has been damaged, which could affect the low temperature crack resistance of asphalt. The creep stiffness modulus of asphalt has been enlarged, and the creep strain rate of asphalt has been decreased after salt freezing cycle. As a result, the low temperature crack resistance and the stress relaxation ability have been reduced. However, the low temperature performance of modified asphalt is better than that of matrix asphalt. It is recommended that the north cold areas as far as possible choose modified asphalt as the pavement material.