Because of fluctuation in leg tension, pitch motion is very effective fatigue and life safety of leg elements in tension leg structures (TLSs). In this paper an exact solution for pitch vibration of a TLS interacting with ocean wave is presented. The legs of TLP are considered as elastic springs. The flow is assumed to be irrotational and single-valued velocity potentials are defined. The effects of radiation and scattering are considered in the boundary value problem. Because of linear behavior of legs during wave excitation, ignoring coupling effects with other degrees of freedom, the analytical solution of pitch response has good agreement with the real behavior of the structure.