A large coronal mass ejection(CME)occurred on July 12,2012,and was associated with an X1.4 flarefrom NOAA AR 11520(S17W08).The CME was propagating toward the Earth,and the whole processwas recorded by the two STEREO spacecraft.We use the STEREO wide-angle imaging observationsand a geometric triangulation technique to determine the CME Sun-to-Earth kinematics,which are thencompared with the associated type Ⅱ radio burst and in situ data acquired from spacecraft in the Sunto-Earth interplanetary space.Solar source characteristics and the in situ flux rope structure are alsoinvestigated,in order to understand the underlying mechanism that controls the whole Sun-to-Earthpropagation of the CME.