In order to study the rheological properties of asphalt mixture, MMLS3 was used to conduct full scale accelerated loading test and PSPA was used to test seismic modulus of upheaval and sag when asphalt mixture came into the stage of flowing deformation. The test results showed that the sag and upheaval changed with different degree of variations under the loads, and the seismic modulus of sag increased gradually and tended to be stable, while the seismic modulus of upheaval decreased gradually. It can be proved that asphalt mixture presents non-uniformity rheological course and the change law of mechanical properties of upheaval is totally different from that of sag.