A giant magnetostrictive semi-active friction energy dissipater comprises sleeves and an outer shell composed of a top cover, a base plate, a left baffle, a right baffle, a front side plate and a rear side plate. One ends of the sleeves are adhered to lower supporting seats arranged on the base plate, the other ends of the sleeves face upper supporting seats arranged on the bottom face of the top cover, and gaps are reserved between the other ends of the sleeves and the upper supporting seats; giant magnetostrictive actuators are arranged in the sleeves, the upper end of each giant magnetostrictive actuator is supported in the corresponding upper supporting seat through a hemispherical supporting upper actuation rod, and the lower end of each giant magnetostrictive actuator is supported in the corresponding lower supporting seat through a hemispherical supporting lower actuation rod; the outer side of the left baffle is connected with a left pull rod through a hex nut, a right pull rod penetrates through the right baffle and is connected with the right side walls of the sleeves, and a baffle is arranged between the left side walls of the sleeves and the left baffle; and a balance pull rod penetrates through the baffle and is connected to the left side walls of the sleeves, and restore springs are arranged between the right baffle and the right sides of the sleeves as well as between the baffle and the left sides of the sleeves. The giant magnetostrictive semi-active friction energy dissipater is quick in response, larger than a piezoelectric ceramic friction energy dissipater in force exerting and various in disassembling and assembling scheme.