The security of Midori-64 under truncated impossible differential cryptanalysis was studied. Firstly, by analyzing the differential paths of Midori in encryption and decryption direction, it was proved that the upper bound for the rounds of impossible differential distinguishers in single-key setting for Midori is 6. And the 6-round truncated impossible differential distinguisher was classified. Secondly, based on the classification, a 6-round distinguisher was constructed. At the same time the impossible differential attack on 11-round Midori-64 was given to recover the 128-bit master key with a time complexity of 2^121.4 11-round encryptions, a data complexity of 2^60.8 chosen-plaintexts, and a memory complexity of 2^96.5 64-bit blocks.