The invention relates to the technical field of preservation of trachinotus ovatus, in particular to a damage-free online preservation method for trachinotus ovatus. The preservation method comprisesthe following steps: killing fresh living trachinotus ovatus, removing internal organs, cleaning the trachinotus ovatus in a cleaning solution, freezing the trachinotus ovatus in an ice box after cleaning, immediately soaking the trachinotus ovatus in a preservation solution after thawing, tightly wrapping the fish body with a preservative film, performing preservation at normal temperature, taking samples irregularly during the period, testing the freshness of the trachinotus ovatus by using a near infrared spectrometer so as to quickly distinguish whether the trachinotus ovatus is fresh or not, and storing the trachinotus ovatus separately. The method can achieve the normal-temperature preservation of the trachinotus ovatus, does not cause the secondary pollution to the trachinotus ovatus, does not damage the tissue of the trachinotus ovatus, is simple to operate, does not need sample processing and expensive instrument, and can quickly distinguish the meat quality of the trachinotusovatus.