It was investigated that the influence of continuous microwave (MW) irradiation during lactation and gestation on the function of learning and memory as well as the role of FT3 and FT4 in this process. 48 SPF KM mice were divided into lactation group, gestation group and control group. All mice were irradiated by MW of 30 mW/cm,2, for 20 min each day except control groups. The gestation group was continuous irradiated until childbirth, about 21days in total. The lactation group was continuous irradiated for 21 days. The blood serum was obtained on the 15 th day of irradiation and then serum FT3 and FT4 were determined by radioimmunoassay. In the gestation irradiation group, FT3 was not significantly changed while FT4 decreased compare to control group. In Place Navigation Test, the escape latency was prolonged in the gestation irradiation group, while there was not significantly changed in the lactation irradiation group. In Spatial Probe Test, the time spent in target quadrants was much longer and the frequency passing through the platform was much more compare to control group. In lactation group, no such change was observed in Morris water maze. The serum FT3 in the lactation irradiation group was decreased while FT4 did not change significantly. The results suggest that continuous MW irradiation during lactation could down regulate serum FT3 level, but could not induce learning and memory function injured. Continuous MW irradiation during gestation could down regulate serum FT4 level and induce learning and memory function injured. The serum TH decrement may be one of the main reasons for learning and memory dysfunction induced by MW.