Abstract: The mesoscale system-relative rear inflow is a component of mesoscale convective systems. It is characterized by a current of air penetrating through the stratiform precipitation region from the rear side of the storm and plays an important role in the formation of a strong cold pool and mesoscale downdrafts. In this study, we have exploited Doppler radar observations,intensive surface observations and NCEP(National Centers for Environmental Prediction) reanalysis to investigate characteristics of the rear inflow in a weak bow echo squall line occurred on 16 May, 2012 in Jiangsu Province. The squall line developed under the combined effects of a northeast cold vortex, a large differential temperature advection, a low-level jet and a thermal ridge. Analysis of the system-relative horizontal winds retrieved from radar radial velocity shows that the rear inflow firstly appeared in the stratiform region in the middle troposphere, and then extended to the back edge of the convective region during the development stage of the squall line. At the mature stage, the rear inflow occupied a continuous channel extending from middle levels at the back edge of the stratiform region to lower levels at the leading convective region. During the dissipation stage,the rear inflow maximum gradually descended to the ground, where it enhanced the local convergence caused by southwesterly inflows and cold pool outflows. This convergence might trigger the formation of new back-building convective cells, thereby causing the occasional dual-band echo. The rear inflow transported the cold and dry air in the middle level to the middle lower convective region, strengthening evaporative cooling and promoting the generation of intensive cold pool outflows and high surface winds. This result is consistent with that of theoretical studies. Under the influence of the maximum rear inflow near the surface and the newly generated band echoes, the cold pool continued to intensify and led to strong surface winds during the dissipation stage. Note that the rear inflow well corresponded to the surface mesoscale convergence line.