The kinetics of conformational transition in the interaction of Ni ion with bovine serum albumin (BSA) was studied using UV-Visible spectrometry and optical rotation measurement. The results showed that the interaction between BSA and Ni ion comprised of two consecutive reactions. The first reaction was a fast coordination reaction between Ni ion and BSA; the second reaction was the conformational transition of BSA induced by Ni ion. The process was not a simple first order reaction reported by previous papers but an opposite reaction, which comprised of a forward first order reaction and reversible first order reaction.