The present study was carried out to investigate the influence of addition of potassium iodide salts on rumen function , thyroid hormones Triiodothyronine (T3) , Thyroxine (T4) , thyroid stimulating hormone (TSH) ,body weight gain ,blood cellular constituent and serum biochemical constituents in goats in Egypt. Fifteen fattening goats belonging to: farm of Faculty of Agriculture , Cairo Univeristy were divided as: Control group (8)only in measurement of body weight gain and experimental group (7). In all other parameters ; experimental group at zero day was the control .Their ages ranged between (6-11 months) in experimental group and (8-9 months) in control group. This study extended to about 2 month at (zero, 15, 30 and 65 days) . Goats drank potassium iodide dissolved in distilled water in the morning with dose 3.8 mg. KI / animal / day. Significant increase in body weight gain and variable significant decrease in T3 and T4 hormones indicating they were still in normal range , changes in blood urea nitrogen and glucose level and changes in hematological parameters.