Abstract: In this paper, taking Penaeus vannamei as the research object, the mechanism of formaldehyde content changing in the Penaeus vannamei storaged at different temperatures was explored. The contents of trimethylamine oxide, trimethylamine, free formaldehyde and reversible combined formaldehyde in samples stored at 20,4,-5 and-20 ℃ were detected termly and their variation tendency were analyzed. The result showed that,at 20,4 and-5 ℃,trimethylamine oxide showed a trend of decrease,corruptive trimethylamine content raised faster as the temperature went higher and free formaldehyde content raised slower as the temperature falled lower. In addition,trimethylamine oxide content gradually reduced and contents of free and reversible combined formaldehyde and free formaldehyde reached up to 6.46 mg/kg,3.09 mg/kg,with maximal increasing slope,in the sample stored for 150 days at-20 ℃,while trimethylamine turned out weak growth only in the late storage stage. At different temperature,the effect of storage time on formaldehyde content changing was significant(p<0.05). Thus it could be seen frozen condition most benefit for keeping penaeus vannamei fresh, but formaldehyde was produced and accumulated most. The study provided with theory support for controlling the formaldehyde producing in frozen storage condition.