To investigate the value of mean platelet volume/lymphocyte ratio (MPVLR) in evaluating the prognosis of primary liver cancer with stereotactic radiotherapy (SBRT). Methods The clinical and follow-up data of 78 patients with primary liver cancer who underwent SBRT treatment in our hospital from June 2016 to December 2018 were retrospectively analyzed. Automatic blood cytometer was used to detect the average platelet volume and lymphocyte level in the patient's serum, and the MPVLR were calculated. According to receiver operating characteristic curve (ROC) analysis, the optimal cut-off value of MPVLR was determined, and multivariate Cox regression analysis was used to analyze the factors that affect the prognosis of primary liver cancer with SBRT. Results ROC curve analysis results show that the AUC(95%CI) of MPVLR predicting the prognosis of primary liver cancer with SBRT treatment was 0.873 (0.764~0.921), and the cut-off value was 5.51. According to the MPVLR cut-off value, patients were divided into low MPVLR group (≤5.51, 31 cases) and high MPVLR group (＞5.51, 47 cases). The proportions of poorly differentiated, tumor diameter＞5.0cm, portal vein tumor thrombus and AFP≥400ng/mL in the high MPVLR group were higher than those in the low MPVLR group (P＜0.05). The 1-, 2-, and 3-year survival rates of patients in the low MPVLR group (87.10%, 77.41%, 67.74%) were significantly higher than those in the high MPVLR group (70.21%, 55.32%, 40.42%) (P＜0.05). The results of prognostic univariate analysis showed that there were significant differences in the 3-year survival rate of patients with primary liver cancer treated with SBRT with different degrees of differentiation, tumor diameter, portal vein tumor thrombus, AFP, and MPVLR (P＜0.05). Multivariate Cox regression analysis showed that MPVLR＞5.51 (HR=2.82, 95%CI:1.43~5.55) was one of the prognostic factors of SBRT treatment for primary liver cancer(P＜0.05). Conclusion MPVLR can be used as a laboratory indicator to predict the prognosis of primary liver cancer with SBRT, and patients with low MPVLR have a better prognosis