Abstract： Objective To determine the correlations of neutrophil?to?lymphocyte ratio(NLR)and platelet?to?lymphocyte ratio (PLR) with the Fletcher grading of gastrointestinal stromal tumors (GIST). Methods Clinical data of 49 patients diagnosed with GIST from February 2005 to December 2012 at the Second Guangdong Provincial People’s Hospital were analyzed retrospectively. We evaluated the correlation of NLR and PLR with maximum tumor diameter,mitotic figures as well as the Fletcher grading. The application of these two parameters for predicting prognostic risk of GIST before surgery was also assessed. Results Significant correlations of NLR and PLR with clinicopathological features of GIST were confirmed , with the higher ratios (NLR>2.4,PLR>132) associating with larger tumor size and more mitotic figures. Also,the two parameters were positively correlated with Fletcher grading system(P<0.05),with higher NLR or PLR suggesting higher Fletcher grades and more invasiveness of GIST. No statistical significance was found between NLR and PLR in predicting prognostic risk of GIST(P=0.445). Conclusion NLR and PLR correlate closely with malignant features and Fletcher grading system of GIST,and therefore can be considered as two feasible novel clinical parameters for predicting tumor prognostic risk.