A method of a flash memory controller includes: controlling an I/O circuit using a set-feature signal, which carries a set-feature command, feature address, and parameter information, and transmitting the set-feature signal to a flash memory device; the feature address corresponds to a valid data portion or a dummy data portion following the valid data portion, and both the valid data potion and dummy data portion are comprised in a full page data which is to be written into a physical page unit of the flash memory device or to be read out from the physical page unit; the corresponding parameter information is used to record the valid data portion's column address and data length, the dummy data portion's column address and data length, the dummy data portion's column address and the valid data portion's column address, or the dummy data portion's data length and the valid data portion's data length.