\documentclass[a4paper]{article}
\usepackage{amsmath}
\usepackage{ctex}
\usepackage{multirow}
\usepackage{amssymb}
\usepackage[left=1.25in,right=1.25in,top=1in,bottom=1in]{geometry}
\begin{document}
\begin{table}
\begin{tabular}{|p{2em}|p{5em}|p{5em}|p{3em}|p{11em}|p{14em}|}
\hline
{} & $F$增加时的$n/mm$ & $F$减少时的$n/mm$ & 平均值$/mm$ & 增重4个砝码时的读数差$\Delta n/mm$ & $\Delta n$\text{的绝对误差} $\Delta (\Delta n)/mm$ \
\hline
$0$ & $n_0$= & $n_0’$= & $\overline{n_0}=$ &\multirow{2}{}{$\Delta n_1$ =|$\overline{n_4}-\overline{n_0}|$=} & \multirow{2}{}{ $\Delta (\Delta n)_1$=|$\Delta n_1 -\overline{\Delta n}$|=} \
\cline{1-4}
$1$ & $n_1$= & $n_1’$= & $\overline{n_1}=$ \
\hline
$2$ & $n_2$= & $n_2’$= & $\overline{n_2}=$ &\multirow{2}{}{$\Delta n_2 =|\overline{n_5}-\overline{n_1}|$=} & \multirow{2}{}{ $\Delta (\Delta n)_2=|\Delta n_2 -\overline{\Delta n}|=$} \
\cline{1-4}
$3$ & $n_3$= & $n_3’$= & $\overline{n_3}=$ \
\hline
$4$ & $n_4$= & $n_4’$= & $\overline{n_4}=$ &\multirow{2}{}{$\Delta n_3 =|\overline{n_6}-\overline{n_2}|$=} & \multirow{2}{}{ $\Delta (\Delta n)_3=|\Delta n_3 -\overline{\Delta n}|=$} \
\cline{1-4}
$5$ & $n_5$= & $n_5’$= & $\overline{n_5}=$ \
\hline
$6$ & $n_6$= & $n_6’$= & $\overline{n_6}=$ &\multirow{2}{}{$\Delta n_4 =|\overline{n_7}-\overline{n_3}|$=} & \multirow{2}{}{ $\Delta (\Delta n)_4=|\Delta n_4 -\overline{\Delta n}|=$} \
\cline{1-4}
$7$ & $n_7$= & $n_7’$= & $\overline{n_7}=$ \
\hline
\multicolumn{4}{|c|}{} &$\overline{\Delta n}$= & $\overline{\Delta (\Delta n)}=$ \
\hline
\end{tabular}
\end{table}
\end{document}