A data writing method for a memory storage apparatus having a first buffer memory, a second buffer memory and a rewritable non-volatile memory module is provided, and the transmission bandwidth of the first buffer memory is larger than the transmission bandwidth of the second buffer memory. The method includes: receiving a write command and first data thereof; determining whether the first data belongs to the successive big data; if the first data belongs to the successive big data, temporarily storing the first data into a first data buffer area of the first buffer memory, writing the first write data from the first data buffer area to the rewritable non-volatile memory module; and if the first data does not belongs to the successive big data, temporarily storing the first data into a second data buffer area of the second buffer memory.