The extratropical transition (ET) process of a tropical cyclone will lead to a variation in the rainfall rate and distribution, which has long been a challenge to weather forecasters. Based on Chinese Meteorological Administration T106 data, satellite observed temperature of black body (TBB) data issued by Japanese Meteorological Administration and the Pennsylvania State University / National Center for Atmospheric Research (PSU/NCAR) numerical model MM5 output, the change of rainfall related to typhoon Winnie (9711) during its ET process is analyzed. Results indicate that the rainfall distribution displays a remarkable asymmetric feature. The heavy rainfall centers occur mainly in the northern part of the typhoon at first, and then move to the northeast and southeastern part of the typhoon circulation, revolving around the typhoon center clockwise during the ET process.Study shows that the change of rainfall distribution is related to the strong vertical shear of horizontal winds in the surrounding environment. It is found that the vertical wind shear is enhanced under the interaction between the typhoon remnant and the upper level westerly trough during the ET process, which is favorable for the rainfall concentration on the left side of downstream of the shear. The locations of heavy rain change clockwise along with the direction of the vertical wind shear. Meanwhile, the vertical structure of the typhoon vortex slants with height, inclining considerably to the north at its transformation stage, then tending to become perpendicular at its re-intensification stage, and inclining to the southeast afterward. We found that the heavy rainfall occurs in the slanting direction of the typhoon vortex. On the other hand, the rainfall locations were also related to the thermal advection activities in the typhoon circulation, which have a good relationship with warm air advection at the lower layer. Moreover, the vertical component of the convective vorticity vector can reflect the impact of the wind vertical shear and mesoscale frontal zone in the ET typhoon circulation synthetically. Its high value area at 800 hPa can indicate the heavy rainfall position within the typhoon circulation.