The present invention provides a kind of quick detecting reagent kit for Laribacter hongkongensis and its detection method. The reagent kit and the detection method is mainly one pair of primers designed based on the 16s RNA conservative fragment of Laribacter hongkongensis. By means of PCR technology, the reaction product shows specific spectral band in agarose electrophoresis. The present invention is used in qualitative detection on the specific DNA fragment of Laribacter hongkongensis in intestinal tract of fresh water fishes, and is simple, fast, specific and sensitive. The present invention is significant in raising the safety on eating fresh water products.