  This is the first article in a series devoted to the study of the asymptotic
expansions of various quantum invariants related to the twist knots. In this
paper, by using the saddle point method developed by Ohtsuki, we obtain an
asymptotic expansion formula for the colored Jones polynomial of twist knots
$\mathcal{K}_p$ with $p\geq 6$ at the root of unity
$e^{\frac{2\pi\sqrt{-1}}{N+\frac{1}{2}}}$.
