Abstract: The paper introduces magneto-rheological damper and its intelligent control method for engineering structural vibration, and points out three existing problems: 1) sedimentation proof stability index can hardly satisfy the requirements for engineering application; 2) the shortages in semi-active control tactics; 3) the advantages of magneto-rheological damper are limited to ordinary dampers. Realizing the problems mentioned above, the paper establishes designing method and fabricating technologies for magneto-rheological fluids. Then, the modified fixed-incremental semi-active control tactics is proposed, whose control effect is better than that of passive-on control tactics. Meanwhile, the paper applies the theory and technologies to solving three kinds of engineering structural vibration control problems which can not be solved by ordinary dampers. Results show that the methods and techniques mentioned in the paper have solved the three problems. This research widens the application of intelligent control by magneto-rheological damper.