  We study gravitational wave production in an expanding Universe during the
first stages following inflation, and investigate the consequences of the
Gauss-Bonnet term on the inflationary parameters for a power-law inflation
model with a GB coupling term. Moreover, we perform the analyses on the
preheating parameters involving the number of e-folds $N_{pre}$, and the
temperature of thermalization $T_{th},$ and show that it's sensitive to the
parameters $n$, and $\gamma$, the parameter $\gamma$ is proposed to connect the
density energy at the end of inflation to the preheating energy density. We set
a correlation of gravitational wave energy density spectrum with the spectral
index $n_{s}$ detected by the cosmic microwave background experiments$.$ The
density spectrum $\Omega_{gw}$ shows good consistency with observation for
$\gamma = 10^{3}$ and $10^{6}$. Our findings suggest that the generation of
gravitational waves (GWs) during preheating can satisfy the constraints from
Planck's data.
