The invention provides a method for improving synthesis of
nucleic acid under a non-diagnostic constant-temperature condition, a kit and application, and relates to the technical field of bioengineering. Provided are: a
nucleic acid having an F2 region capable of annealing with F2c in an F region on the same chain at the 3'end, and an R2
c region capable of annealing with R2 in an R region on the same chain at the 5 'end; taking the
nucleic acid as a template, taking the 3'end of the F1
c region annealed with the F1 region as a synthesis starting point, and synthesizing a complementary nucleic acid chain of the nucleic acid; and performing complementary chain synthesis through a
polymerase catalytic chain displacement
type synthesis reaction so as to replace the complementary nucleic acid chain synthesized in the previous step. The method has the main
advantage that a new combination of short-chain primers can be obtained through simple transformation to trigger rapid amplification of
gene fragments by applying a single-
enzyme constant-temperature
system to short-chain nucleic acid fragments.