Abstract： Objective To evaluate the predictive value of proton magnetic resonance spectroscopy (1H-MRS)and diffusion weighted imaging(DWI)in low-grade cerebral astrocytomas. Methods Twenty patients with histological proved low-grade astrocytomas treated with postoperative radiotherapy were evaluated with cMRIMRS, DWI before-and 3 months after radiotherapy respectively, then repeated every six months. rNAA,rCho,rCr,rADC was the ratio of NAA, Cho and Cr in the residual tumors region to the those of normal control region. The difference of rCho/rCr, rCho/rNAA, rADC between deteriorative group(group Ⅰ)and stable groups(group Ⅱ)were calculated both before-and 3months after radiotherapy. Results The value of rCho/rCr, rCho/rNAA were higher in group 1 than those in group Ⅱ 3 months after radiotherapy(t =3.65 and 4. 24,all P ＜ 0. 05), while the value of rADC was lower in group Ⅰ(t = 3.43, P ＜ 0. 05). The mean difference of rCho/rCr,rCho/rNAA, rADC in group Ⅰ were smaller than those in group Ⅱ(t = 2. 02,4. 21 and 3.00,all P ＜0. 05). The value of rCho/rCr,rCho/rNAA increased and rADC decreased gradually in group Ⅰ during follow up, and these patients were histologically proved recurrence within 11 - 16 months.While in group Ⅱ , the value of rCho/rCr, rCho/rNAA decreased and rADC increased gradually or steady.And also with a stable clinical performance and cMRI. Conclusions 1H-MRS and DWI own better predictive value of monitoring tumor metabolism change, growth potential and evaluation response to radiotherapy than conventional MRI in low-grade group astrocytomas.