Dynamic characteristics and control performance for structures with pseudo-negative stiffness and viscous dampers are studied. First, dynamic characteristics are analyzed by transmissibility and dynamic magnification factor of structures with pseudo-negative stiffness and viscous dampers. Second, control performance for structures with pseudo-negative stiffness and viscous dampers subject to earthquake excitation is studied by response spectrum, and it is compared with control performance for structures with viscous dampers. The results show that pseudo-negative stiffness control system can change equivalent period of structure; control effects of absolute acceleration and displacement for structures with pseudo-negative stiffness and viscous dampers are better than those of structures with viscous dampers when period is longer.