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An YBCO sample with high critical current density or single crystal stracture, can be obtained by the directional solidification method. In the present paper the morphology and chemical composition at the growth front of YB CO crystal have been investigate in order to it make clear the stopped growth mechanism of YBCO crystal growth during melt growth moment of the directional solidification. It is found that YBCO crystal will cease growing when yttrium and barium are depleted and copper becomes rich element in the liquid phase at the YBCO crystal growth front. For maintaining the continuous growth of YBCO, the composition of Y, Ba and Cu in raw sample has to be adjusted so as to make yttrium and barium enrichments in the liquid phase at the YBCO crystal growth front during the melt growth process.