A data writing method for writing data from a host system into a flash memory chip having a plurality of physical blocks is provided. The method includes configuring a plurality of logical access addresses and recording address centers and address radiuses for the physical blocks. The method also includes receiving data to be written in logical access addresses, determining opened physical blocks among the physical blocks, and writing the data into the flash memory chip based on the logical access addresses, and the address centers and the address radiuses of the opened physical blocks. Accordingly, the method can effectively reduce the degree of data dispersion of each of the physical blocks, reduce the time for organizing valid data, and increase the speed for writing data.