The invention discloses a nucleic acid isothermal amplification method by polymerase spiral reaction (PSR). A pair of oligonucleotide primers is used, mutually reverse nucleotide fragments are added to 5' ends of the primers, a target gene is subjected to PSR under the action of the primers and deoxyribonucleic acid (DNA) polymerase and under the isothermal condition, self-spiral extending of the target gene can be achieved, and thereby, nucleic acid amplification can be finished. According to the nucleic acid isothermal amplification method by PSR, a novel technology platform is provided for nucleic acid detection, amplification of a product is simple, an amplification product is applicable to the field of detection and can be slightly processed to be subjected to clone recycling and sequencing, the method can be applied to all fields which require nucleic acid amplification, the market prospect is wide, the economic and social benefits are large, and the method is suitable for large-range popularization and application.