  All solutions of constant classical Yang-Baxter equation (CYBE) in Lie
algebra $L$ with dim $L \le 3$ are obtained and the sufficient and necessary
conditions which $(L, \hbox {[ ]}, \Delta_r, r)$ is a coboundary (or
triangular) Lie bialgebra are given. The strongly symmetric elements in
$L\otimes L $ are found and they all are solutions of CYBE in $L$ with $dim L
\le 3$.
