A method for performing block management is provided. The method is applied to a controller of a Flash memory having multiple channels. The Flash memory includes a plurality of blocks respectively corresponding to the channels. The method includes: temporarily storing at least one index of at least one good block that is not grouped into any meta block into a spare good block table, where the good block is a block that is not determined as a bad block within the plurality of blocks; and when it is detected that a specific block corresponding to a specific channel within blocks currently grouped into meta blocks is a bad block, dynamically updating the spare good block table for use of block management. In particular, when needed, the good block is utilized for replacing a block grouped into a meta block. An associated memory device and a controller thereof are also provided.