To explore mechanism and feasibility of “lock in freshness” of farmed fish chilled products, Takifugu rubripes farmed was taken as raw material. The experiment is performed in two post mortem stages, including a quality determination period（QDP）corresponding to on-site handling and post quality determination period (P-QDP）corresponding to the ice storage. The delayed effect of the QDP chilling treatment on the P-QDP was investigated. On-site handling were carried out using humane slaughter followed by instant bleeding in -1℃ sea water with 20 minutes, gutted and rinsed fish were individually wrapped and storaged with flake ice surrendered. Meanwhile, the Control group as chilling-free was compared to the Treatment group with chilling at the QDP. The chilled Takifugu rubripes postmortem biochemical metabolism was measured by rigor index, pH, lactic acid content, ATP and ATP-related compounds and K-Value. Meanwhile, the quality was performed and analyzed by muscle ultrastructural changes in two treatments. Result showed that Treatment temperature after chilling in quality determination period dropped rapidly from 10.9℃ to 2.7℃ in 20 minutes, which has a significantly effective of chilling. Treatment temperature was increased dramatically from 2.7℃ to 8.5℃ in 1 hour because of the special strengthening washing body process of Takifugu rubripes after processed. And the fish temperature was reduced to 0.5℃ after 12h iced storage. The delayed effect of the QDP chilling treatment on the P-QDP can be clearly observed by the muscle ultrastructural. Regardless of the Treatment or the Control, in subsequent chilling storage, muscle tissue degraded gradually. Notable, distinct difference can be observed between the Treatment and the Control. The phenomenon of cell structure degraded of the Control was occurred compared with the Treatment in day 0. And intermyofibrillar spaces increased were occurred. Sarcomeres were non-parallel and swollen sarcoplasmic reticulum was obviously. Especially in day 4, sarcomeres were altered significant, mainly at the Z-line and I-band level disruptions. Structure was obscured and destroyed more significantly than the Treatment. But the results showed that traditional biochemical indictors could not be detected sensitive difference of the two treatments. The Treatment biochemical metabolism rate was keep pace with the Control: the rigor mortis progression was similar and rigor state was maintained 4-5 days. Lactate acid, pH, nucleotide metabolism rate and K-value had no significant difference, and K-value was 15% in 8th chilling storage. In conclusion, there was a quality determination period after fish captured, which had the delayed effect of chilled fish quality on the post quality determination period. The degradation of muscle cell could be prolonged by QDP-chilling, which had significant effect of “lock in freshness” on quality of chilled fish. In this way, the image of seafood quality of domestic fisheries could be improved fundamentally, providing significant practical value in China.