The present invention provides a primer for nucleic acid random fragmentation and a nucleic acid random fragmentation method. The primer consists of a plurality of upstream random primers and downstream random primers. The sequence composition of the upstream random primers is 5′-X-Y-3′, and the sequence composition of the downstream random primers is 5′-P-Y′-X′-close-3′, wherein Y and Y′ are random sequences, X is all or part of sequences of a sequencing platform 5′ end adaptor, X′ is all or part of sequences of a sequencing platform 3′ end adaptor, P is phosphorylation modification, and close is close modification. The primer of the present invention adopts double random anchoring of both the upstream random primers and the downstream random primers, and a DNA sample can be randomly broken.