Objective This study aimed to identify laboratory indicators with significant implications for bone marrow invasion in gastric cancer patients and to evaluate their prognostic value. Methods A retrospective analysis of the clinical data of 320 gastric cancer patients who underwent either bone marrow cytological examination or bone marrow biopsy at our hospital between January 2013 and December 2023 was conducted. Among these patients, 31 patients with confirmed bone marrow invasion composed the study group, whereas 34 stage IV gastric cancer patients without bone marrow invasion composed the control group. Differences in demographic and laboratory data between the two groups were compared. Receiver operating characteristic curves were used to identify valuable indicators for predicting bone marrow invasion in patients with gastric cancer. Survival analysis was performed using the Kaplan-Meier method and included the plotting of survival curves. Additionally, Cox proportional hazards regression analysis was performed to evaluate independent prognostic factors. Results Significantly different values (all P < 0.05) were observed for age, peripheral blood immature cells, Hb, PLT, SII, FIB, PT, FDP, D-Dimer, FDP/FIB, CEA, and CA72-4 between stage IV gastric cancer patients with and without bone marrow infiltration. The ROC analysis indicated that at a threshold value of 5.197 for FDP/FIB, the AUC was 0.958 (P < 0.01). Within the cohort of 65 stage IV gastric cancer patients, those with bone marrow invasion and high FDP/FIB ratios exhibited notably shorter median survival times than those without bone marrow invasion and with low FDP/FIB ratios (chi 2 = 25.928, 20.128, P < 0.001). Multivariate analysis demonstrated that bone marrow invasion (HR = 4.148, P = 0.020) and the FDP/FIB ratio (HR = 1.026, P = 0.024) were independent risk factors influencing the prognosis and survival outcome of stage IV gastric cancer patients. Among the subset of 31 gastric cancer patients with bone marrow invasion, the median survival time for the high FDP/FIB group was 22 days, which was significantly shorter than the 60 days observed in the low FDP/FIB group (chi 2 = 8.479, P = 0.004). Conclusion The FDP/FIB ratio can serve as an important indicator for the diagnosis and prognostic evaluation of bone marrow invasion in patients with gastric cancer.