Method for screening bad column and data storage device with bad column summary table

A data storage device for storing a bad column summary table, wherein the data storage device comprises a control unit and a data storage medium, the data storage medium comprises a plurality of data blocks, each of the data blocks comprises a plurality of columns divided into a plurality of segments, each of the data blocks further comprises a plurality of data pages, each of the data pages comprises the columns arranged in a same row, and the bad column summary table is generated and updated according to steps of:

• reading out written data of at least one of the data pages of at least one the data blocks;
• comparing the written data with predetermined data to obtain a number of error bits in each of the columns in each of the segments in the at least one of the data pages, and accordingly calculating a total number of error bits in each of the segments;
• determining a segments having a largest total number of error bits from the segments;
• and
• determining and recording a columns having a largest number of error bits from the segment having the largest total number of error bits as a bad column.