A memory management method is provided. The method includes selecting a target physical programming unit; using a first read voltage corresponding to a first type physical page of the target physical programming unit to read a plurality of target memory cells of the target physical programming unit, so as to calculate a first bit value ratio; if the first bit value ratio is not smaller than a first preset threshold, using a second read voltage corresponding to the first type physical page of the target physical programming unit to read the plurality of target memory cells of the target physical programming unit, so as to calculate a second bit value ratio; and determining whether the first type physical page of the target physical programming unit is empty by comparing the first bit value ratio and the second bit value ratio.