For the translocation of a diblock copolymer chain through a nanopore on a membrane with two translocation orders, the free energies under different conditions are given, and then the mean first-passage time (MFPT) is obtained by solving the Fokker-Planck equation. By the corresponding numerical calculations, it is shown that, when the copolymer chain transports from the region of good solvent to that of poor solvent, the translocation order that the block without coil-blob transition transports first is prior to the other. At a given order, it is found that the chemical potential, coil-blob transition, composition of the diblock copolymer chain and the translocation rate play an important role in the translocation. The present studies are expected to provide available clues for the translocation of real biopolymer chain.

Key words: diblock copolymer chain, translocation, mean first-passage time (MFPT), coil-blob transition