  We study the first law of thermodynamics in IR modified H\v{o}rava-Lifshitz
spacetime. Based on the Bekenstein-Hawking entropy, we obtain the integral
formula and the differential formula of the first law of thermodynamics for the
Kehagias-Sfetsos black hole by treating $\omega$ as a new state parameter and
redefining a mass that is just equal to $M_{ADM}$ obtained by Myung\cite{YSM2}
if we take $\alpha=3\pi/8$.
