To further clarify the effect of lethal conditions on the quality of grouper(Epinephelus lanceolatus) and to improve the quality of grouper during refrigeration, five different lethal methods were used to treat grouper, with the following groups: Ⅰ: lethal by ice burial; Ⅱ: lethal by knocking on the head; Ⅲ: lethal by subjecting live grouper to temperature gradients of 18, 14, 10 and 6 ℃ (each temperature treatment for 20 min); Ⅳ: lethal by subjecting live grouper to temperature gradients of 18, 12 and 6 ℃ (20 min at each temperature); Ⅴ: lethal by subjecting live grouper to temperature gradients of 18, 6 ℃ (20 min at each temperature). The grouper was then rapidly reduced to 0 ℃ in the centre of the fish body by micro-freezing machine and refrigerated at 0-4 ℃. The effects of changes in the sensory evaluation, textural characteristics, pH, lactic acid content, sulfhydryl content, volatile salt nitrogen (TVB-N), total bacterial colony count and other quality evaluation indicators of the fish during the freezing period were subsequently measured and analyzed. The results showed that the five groups of lethal treatments had significant effects on the quality of fish meat during refrigeration, in descending order: sensory evaluation and TVB-N: group Ⅴ> group Ⅰ> group Ⅱ> group Ⅳ> group Ⅲ, texture: group Ⅳ> group Ⅴ> group Ⅱ> group Ⅰ> group Ⅲ, lactic acid content and pH: group Ⅴ> group Ⅰ> group Ⅱ> group Ⅳ> group Ⅲ, sulfhydryl content and total bacterial colony: group Ⅰ> group Ⅱ> group Ⅴ> group Ⅳ> group Ⅲ. ＞ group Ⅳ＞ group Ⅲ. This indicated that the lethal treatment by gradient cooling was significantly better than the lethal treatment by head knocking and ice burying, and the temperature difference interval in gradient cooling should not be too wide. The results of the quality evaluation of all the indicators showed that group Ⅲ had the best lethal treatment, as the narrower temperature range made the process of grouper death less stressful, and the lactic acid content, pH and total sulfhydryl group were relatively stable, which was more effective than the other four groups in delaying the reduction of textural characteristics and sulfhydryl group content and inhibiting microbial activity, thus prolonging the shelf life of the fish samples.