An unprecedented synthesis of polysubstituted pyrrolidines from anilines and diazo pyruvates by ruthenium catalysis under mild reaction conditions is reported. An enol intermediate derived from the N-H insertion of aniline toward the ruthenium carbene species as well as an imine ester intermediate generated by SET-mediated oxidation of enol were proposed as the key intermediates. This strategy provides various pyrrolidines containing four contiguous stereocenters in good efficiency with high diastereoselectivities.