please help me i can't resolve this problem
the problem is character _t
\documentclass{article}
\usepackage{array,booktabs ,tabularx,multirow}
\usepackage{fontspec}
\usepackage{arabxetex}
\newfontfamily\arabicfont[Script=Arabic , Scale=1.5]{Nazli}
\begin{document}
\begin{tabularx}{\textwidth}{|r ||||X|||| r |}
\toprule
\textarab{AlmdT AlzmnyT : sA`tAn} & \centering \textarab{{\LARGE Al-'imt.hAn Al|m|.hly Al|m|w.hd }} & \textarab{'i`dAdyT `bd Alkrym Alx.tAby } \\
\textarab{AldwrT : $II$}& \centering \textarab{\Large{fy m|AdT AlryA.dyAt}}&\textarab{nyAbT tAwryrt} \\
\textarab{Alm`Aml : $3$} & \centering \textarab{AlsnT Al_tAl_tT 'i`dAdy} & \textarab{dabdw} \\
\bottomrule
\end{tabularx}
\end{document}

tabularxnecessary for the example? Can you reduce to a minimum that still describes the issue? – egreg Sep 16 '14 at 22:07