A method for accessing data by a solid state disk is provided, which includes steps of: configuring at least one NAND die to be dedicated for writing random data and other NAND dies to be dedicated for writing sequential data; configuring one of the NAND dies dedicated for writing the sequential data to include memory cells each of which is allowed to be used for storing a data stream having the maximum number of bits; configuring one of the NAND dies dedicated for writing the random data to include memory cells each of which is used for storing a data stream having the number of bits that is smaller the maximum number of the bits; and determining the total number of the bits of one of the data streams of the random data written by the NAND dies and accordingly reconfiguring the NAND dies.