  In this paper, we consider the Klein-Gordon-Schr\"{o}dinger system with the
higher order Yukawa coupling in $ \mathbb{R}^{1+1} $, and prove the local and
global wellposedness in $L^2\times H^{1/2}$. The method to be used is adapted
from the scheme originally by Colliander J., Holmer J., Tzirakis N.
\cite{CoHT06} to use the available $L^2$ conservation law of $u$ and control
the growth of $n$ via the estimates in the local theory.
