Abstract: In this paper, we have studied behavior of borate during solar evaporation of brine. The solar evaporation of the borate-containing brine indicates that the crystallization of salts does not accord with Van'thoff's stable equilibrium diagram, but agrees with Kurnakov's solar evaporation diagram.The number of concentrated times of brine (W⁰_brine/W_brine) equals to that of boron enrichment (C_boron/C⁰_boron) in concentrated brine during solar evaporation. It may be considered that the borate does not generally crystallize out till the stage of bischofite, and accumulates fully in the concentrated brine.