Objective The aim of the study was to investigate and compare the prognostic value of advanced inflammatory index, platelet/lymphocyte ratio (PLR), and Ki-67 expression in stage Ⅲ–IV inoperable non-small cell lung cancer (NSCLC) before treatment. Methods The clinical data of 98 inoperable patients with stage Ⅲ–IV NSCLC in our hospital (Fifth Department of Oncology, Hebei General Hospital, Shijiazhuang, China) before treatment were retrospectively analyzed, and advanced lung cancer inflammation index (ALI) was calculated using body mass index (BMI) × serum albumin (ALB) ÷ neutrophil/lymphocyte ratio (NLR). he optimal cutoff values of ALI and PLR for predicting prognosis is determined. Chi-square test was used to analyze the relationship between patients and clinical characteristics. Kaplan-Meier method was used to calculate the total survival of patients, and log-rank test was used for comparison. Independent prognostic factors were assessed by univariate and multivariate analyses. Spearman correlation was used to analyze the relationship among ALI, PLR, and Ki-67. Results In our study of the 98 cases, the survival time of the patients with ALI 18 (P < 0.001), with a median survival time of 10 months and 25 months, respectively. The survival time of patients with a PLR 185 (median survival time was 27 months vs. 10 months, P < 0.001).The higher the Ki-67 expression, the shorter the survival time (P < 0.005).The combined ALI and PLR detection results indicated that the survival time of patients with high ALI and low PLR was significantly longer than that of patients with low ALI and high PLR (P < 0.001). Univariate analysis showed that smoking history, degree of differentiation, KPS score, Ki-67 expression, ALI value, and PLR affected the prognosis of patients. Multivariate analysis showed that KPS score, ALI value, and Ki-67 expression were independent prognostic factors. Conclusion ALI, PLR, and Ki-67 expression are important predictors of stage Ⅲ-IV inoperable NSCLC. In terms of the prognostic value, ALI seems to have the best ability to predict patient survival. In addition, the combined detection of ALI and PLR levels before treatment seems to be more helpful in improving our prediction of patient prognosis. Moreover, it is expected to play a role in future clinical applications.