Using the high micro-Raman spectroscopy, the micro-structures of nonlinear optical crystal LiB3 O5 and its high temperature solution were studied. The high temperature Raman spectra of LiB3 O5 crystals, Raman spectra of lithium borate glasses Li2 O·4B2 O3 at room temperature and its melt at high temperature were obtained. The analysis of these spectra indicates that the micro-structures of LiB3 O5 crystal and lithium borate glasses Li2 O·4B2 O3 are mainly the six-number boroxol rings containing one B
tetrahedron (represents bridge oxygen). With the temperature increasing, the stability of B?4 tetrahedron decreases and destroys, a conversion from 4-coordinated boron B
to 3-coordinated boron B occurs. As a result, the six-number boroxol rings containing one B
are partly destroyed and the concentration of boroxol B3
in the high temperature solution increases. The structural characteristics of the high temperature Li2 O·4B2 O3 solution are benefit for LiB3 O5 crystal growth.