One scanning method of transform-based digital data processing includes: when processing data blocks, recording characteristics information for different block categories individually; conditionally adjusting scan orders of data processing of the block categories according to the characteristics information; and performing the data processing upon a current data block according to a scan order corresponding to a block category to which the current data block belongs. Another scanning method of transform-based digital data processing includes: recording characteristics information when processing data blocks; conditionally adjusting a scan order according to the characteristics information; keeping at least one position in the scan order fixed regardless of changes made to the scan order; and performing a data processing upon a current data block according to the scan order.