Objective：The current study aims to evaluate the correlation between inflammatory markers and 18F-fluorodeoxyglucose (FDG)positron emission tomography/computed tomography(PET/CT)metabolic parameters in patients with small cell lung cancer (SCLC)at baseline. Methods：A total of 56 SCLC patients，who underwent 18F - FDG PET/CT and did not receive any treatment in Department of Nuclear Medicine，the First Affiliated Hospital of Nanjing Medical University between January 2014 and December 2019，were analyzed retrospectively. The inflammatory markers[neutrophil/lymphocyte ratio(NLR)，platelet/lymphocyte ratio(PLR)， monocyte/lymphocyte ratio(MLR)and systemic immune-inflammation index(SII)]，clinical data and metabolic parameters of primary tumor[maximum standardized uptake value(SUVmax)，mean standardized uptake value(SUVmean)，metabolic tumor volume(MTV)，TLG(total lesion glycolysis)]within one week before PET/CT detection were collected to analyze the correlation by Spearman’s rho test. Results：The slight positive correlations were found between inflammatory markers(NLR，PLR，MLR，SII)and partial metabolic parameters[TLG(r_NLR=0.309，r_PLR=0.304，r_MLR=0.271，r_SII=0.362)，MTV(r_NLR=0.354，r_PLR=0.341，r_MLR=0.290，r_SII=0.411)]of primary tumor in 56 patients with SCLC(all P ＜ 0.05). The SUVmax and SUVmean were not found to be correlated with these hematological parameters(all P ＞ 0.05). The neutrophils，NLR，MLR，SII，MTV and TLG in extensive stage were higher than those in limited stage， and the lymphocytes in extensive stage were lower than those in limited stage(all P ＜ 0.05)，but SUVmax，SUVmean，PLR，monocytes and platelets were not found differences between extensive and limited stage(all P ＞ 0.05). Conclusion：Baseline NLR，MLR，SII of SCLC not only reflect the systemic metabolism，but also reflect the local inflammation of tumor. It may be necessary to receive whole- body PET/CT for staging to adjust treatment strategy in those patients with high NLR or MLR，SII.