The invention discloses a primer group for NPT(Noctumal Penile Tumescence)II gene detection, which consists of an outer primer F3, an outer primer B3, an FIP (Forward Inner Primer) and a BIP (Backward Inner Primer); nucleotide sequences of the outer primer F3, the outer primer B3, the FIP and the BIP are respectively shown by SEQ (Sequence) ID (Identity) No. 1-4 or SEQ ID No. 5-9. The primer group has the beneficial effects that whether a target substance exists or not can be judged according to whether to amplify or not, and the specificity is high. The invention also discloses a reagent kitfor detecting a NPTII gene, which comprises two pairs of primers, i.e. an FIP / BIP and an outer primer F3 / B3, which takes the NPTII gene as a target gene and is designed based on a loop-mediated isothermal amplification technology. The reagent kit has the beneficial effects that the NPTII gene can be quickly detected, the amplification can be carried out only by one constant temperature, a specialreagent or equipment is not required, the detection cost is low, and moreover, the sensitivity and the specificity are high. Meanwhile, the invention also discloses a use method of the reagent kit.