The present invention relates crystalline form of GnRH receptor antagonist and a preparation method thereof. In particular, the present invention relates a type I crystal of 1-(4-(7-(2,6-difluorobenzyl)-3-((dimethylamino)methyl)-5-(6-methoxypyridazin-3-yl)-4,6-dioxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-d]pyrimidin-2-yl)phenyl)-3-methoxyurea(compound of formula (I)) and a preparation method thereof, pharmaceutical use thereof, and type I crystal of formula (I) and pharmaceutical composition in the preparation of a medicament for treating GnRH receptor antagonist related diseases. The type I crystal of formula (I) obtained by the present invention has good stability, and the used crystal-solvent has a low toxicity and residue, which can be better used in clinical treatment.本發明涉及一種GnRH受體拮抗劑的結晶形式及其製備方法。具體地，本發明涉及1-(4-(7-(2,6-二氟苄基)-3-((二甲胺基)甲基)-5-(6-甲氧基噠嗪-3-基)-4,6-二羰基-4,5,6,7-四氫-2H-吡唑並[3,4-d]嘧啶-2-基)苯基)-3-甲氧基脲(式(I)化合物)的I晶型及製備方法，其在醫藥組成物的應用以及該I晶型和組合物在製備治療具有GnRH受體拮抗劑有關疾病中的用途，本發明所得到式(I)化合物的I晶型具備良好的穩定性，並且所用結晶溶劑低毒低殘留，可更好地用於臨床治療。
