331 Background: Myeloid Deprived Suppressor Cell (MDSC) has been recoganized as a promising target for hepatocellular carcinoma (HCC). However, targeted therapy on MDSC failed to display convincing efficacy. Optimization of patient selection to find the most potential beneficiaries might be a solution to this issue. In the present study, we aimed to identify clinical parameters relevant to MDSC level in HCC patients for future MDSC targeted therapy. Methods: In the present study, a series of 55 HCC patients (prospective group) and 20 healthy donors were analyzed investigating frequencies of MDSC in peripheral blood mononuclear cells (PBMC). Results: As a result, we found that MDSC level was increased in HCC patients compared to healthy donors (10.33% vs 1.54%, p< 0.0001). The monocytes (r2= 0.2875, p< 0.0001), neutrophils (r2= 0.3630, p< 0.0001) and platelet counts (r2= 0.0828, p= 0.0331) in circulation was positively associated with MDSC level. Then, the prognostic value of the above predictors was determined in a retrospective database of 243 HCC patients (retrospective group). The baseline characteristics of prospective and retrospective group were similar. Platelet-to-lymphocyte ratio (PLR) were confirmed to be an independent predictor for OS ( p= 0.003) with the rest parameters presented negative results. Then, advanced HCC patients were divided into two groups based on PLR value ≤111.23 or > 111.23 according to ROC analysis. Patients with low PLR presented higher 3-month survival rate (57.6% vs 37.6%) compared with patients with high PLR. PLR was associated with aggressive behavior of malignancies, such as distant metastasis and portal vein thrombosis. Conclusions: In summary, the present study firstly indentified blood platelet counts was a predictor of MDSC level in PBMC for HCC patients. And, patients with higher PLR might be the optimal patient subgroup for MDSC targeted therapy.