Objective:To elucidate the role of antisense oligodeoxynucleotide of p55PIK inhibiting the proliferation of thyroid carcinoma cells. Methods:The lentivirus package system carrying the antisense RNA of p55PIK was constructed. The FTC236 cell was infected by the virus. Western blot and Realtime PCR were used to confirm the protein content and mRNA level of p55PIK. Then MTT assay and BrdU/PI corporation assay were used to analyze the proliferation of stable cells. Results:Two stable cell lines,one expressing p55PIK antisense RNA and the other expressing scramble antisense RNA,were constructed,and the p55PIK antisense RNA could knockdown the target protein’s expression(P < 0.01). In MTT assay,the absorbance ratio of the cells expressing p55PIK antisense RNA is (59 ± 19)% of that in the cells expressing scramble antisense. The BrdU/PI corporation assay showed that the DNA synthetize ratio of cells expressing p55PIK antisense RNA decreased by 11.6% compared with that of cells expressing scramble antisense. Conclusion:The p55PIK antisense can inhibit proliferation of the thyroid carcinoma cells by knockdown the p55PIK protein expression.