Abstract: To test the hypothesis that the sympathetic nerve plays a crucial role on the level of 17β-estradiol, progesterone and the number and activity of mast cells in the uterus during early pregnancy and the sympathectomy mouse was established by 6-hydroxydopamine (6-OHDA) treatment. Levels of 17β-estradiol and progesterone in serum were determined by radioimmunoassay and mast cells number by histochemistry and histamine content using fluorospectrophotometry. Compared with the control, the number of embryos decreased by 64.4-69.9% in the treated groups and the level of 17β-estradiol was significantly increased at embryonic days (E3) and E9, while it was decreased at E1, E5 and E7. The level of progesterone in the treated group was increased during E1-E5, with peak elevation of 2 folds at E3. The number of mast cells was highest at E3 in both the control and treated mouse. However, it was significantly increased in the treated group by 136.03, 24.54 and 177.97% at E5, E7 and E9, respectively. However, the change in histamine content was significantly decreased 7.5-fold at E3, but increased at E7 and E9 in the treated group; it was near the limit of the detection line in the control at E7 and E9. It can be concluded that the sympathetic nerve has an effect on the synthesis and secretion of sex hormones and regulates mast cells in the uterus during early pregnancy, especially in implantation period.