A memory storage device, a memory controller thereof and a data transmission method thereof are provided. The memory storage device includes a rewritable non-volatile memory module having a first and a second memory dies, and the first and the second memory dies are coupled to the memory controller through the same data input/output bus. The method includes transmitting a read command to the first memory die and then transmitting a write command to the second memory die by the memory controller. The method further includes controlling the first and the second memory dies to respectively read out and put data onto the data input/output bus in accordance with the read command and write the data from the data input/output bus into the second memory die in accordance with the write command at the same time by the memory controller.