Abstract: The objective of this study was to determine the effects of chelated chromium (chromium-picolinate or chromium-lysine ) supplementation on lactation performance and some blood components of Holstein cows during the lactating period. Seventy five multiparous lactating Holstein cows (80 days post-partum) used in this study were divided equally into three groups (25 cows/treatment) and were randomly allocated to one of three treatment diets. Diet A, basal diet, with chromium-picolinate added at manufacturer’s recommended level (0.6 g /head per day). Diet B, basal diet, with chromium-lysine(0.076 g /head per day). Diet C, was basal diet without chromium (Cr) added and served as a control. The result of this study showed the supplement of chromium to the diet of cattle contributed to the increase of milk yield and may contribute to the improvement of the immune status of stressed dairy cows. In comparison with the diet C, milk production of diet A and diet B were both increased（P<0.01）,insulin concentration in blood of diet A led to depressed（P<0.01）and glucose concentrations in blood of diet A and diet B were higher than that of treatment diet C（P<0.01）.The mean Cortisol concentration in blood of diet A and diet B decreased by 7.21 nmol/L, 4.92 nmol/L, respectively, and the mean IgG concentration in blood of diet A and diet B increased by 2.1 g/L and 3.1 g/L , respectively, compared with diet C.