  In this paper, we give the general crossing relation for boundary reflection
matrix $R(\beta)$, which is the extension of the work given by Ghoshal and
Zamolodchikov .We also use the first non-trivial extended crossing relation to
determine the scaler factor of $R(\beta)$ which is the rational diagonal
solution to the boundary Yang-Baxter equation in the case of l=2 and n=3.
