Disclosed are a nucleic acid fragmentation method and a sequence combination. The method comprises the following steps: subjecting a denatured nucleic acid to annealing and an extension reaction by using a single-stranded 5′-end extension primer, wherein the single-stranded 5′-end extension primer comprises a sequencing platform adaptor sequence of a 5′ end and a connected random sequence, and the random sequence is subjected to annealing on a random site of the denatured nucleic acid; and directionally connecting a double-stranded 3′-end adaptor sequence to the 3′ end of the nucleic acid generated in the extension reaction, and carrying out denaturalization and purification to obtain a fragmented single-stranded nucleic acid with adaptor sequences on two ends.