In this paper, a nonlinear energy sink with piecewise linear stiffness spring is proposed, and the fundamental characteristics of the nonlinear energy sink are investigated. Firstly, the structure of the piecewise linear stiffness spring is proposed and nonlinearity of the spring is analyzed. Then, the dynamic model of the primary vibration system with the nonlinear energy sink is built, and the responses and vibration suppression effects are studied by numerical simulations. Finally, the effectiveness of the NES is proved by experiment. The results show that the piecewise linear stiffness spring is effective; its structure is simple, compact and adjustable; the vibration attenuation performance of nonlinear energy sink is very good under moderate exciting force.