Abstract: Objective: In order to investigate the effect of IL-1 β on the inositol phosphate （Inos）/Ca²⁺ cascade in thyroid cells, the changes of cytosolic Ca²⁺ induced by IL-1 β and TSH were observed by laser scanning confocal microscope（LSCM） in rat thyroid FRTL-5 cells.Methods: The cultured FRTL-5 cells loaded with Ca²⁺ probe Fluo 3 were exposed to the different concentrations of TSH or IL 1β and then the cytosolic Ca²⁺ were measued by LSCM. Results: The intracelular Ca²⁺ levels of FRTL-5 cells were increased after adding TSH（1 to 5U/L） by dose dependent manner; while IL 1β decreased the basal levels and the TSH stimulated effect of cytosolic Ca²⁺ . Conclusion: TSH may elevate cytosolic Ca²⁺ levels, indicating that Ca²⁺ can mediate the action of TSH on thyroid cells; IL-1β has a direct inhibitory effect on Inos/Ca²⁺ cascade in thyroid cells.