Objective:To measure the metabolite value and the index value in patients with brain metastases before and after radiotherapy by using MRS,analyze the relevance between the values and the volume of the tumor tissue.Methods:Thirty-three patients with brain metastasis from pathologic confirmed lung cancer were treated by LINAC radiosurgery in combination with WBRT.21 cases were included in this group.All cases were underwent examination of MRS before treatment,1 day,1 week,1 month,3 months and 6 months after treatment.The comparison of the examined values of MRS between the two groups and analysis the relevance between the tumor volume and the values was undertaken.Results:Cho、Cho/Cr、Cho/n Cho had significant the positive relevance between the values and the volume of the tumor tissue(P<0.05).Conclusions:Cho was the most important index that could respond the metabolism of tumor.The variation of Cho had inherent relationship with volumes of tumors.