Abstract: Objective To investigate the clinical efficacy of low molecular heparin calcium combined with rivaroxaban in the treatment of elderly patients with advanced lung cancer complicated with pulmonary embolism. Methods Totally 84 elderly patients with advanced lung cancer complicated with pulmonary embolism were selected and randomly divided into observation group and control group, with 42 cases in each group. The control group was treated with low molecular heparin calcium combined with warfarin, while the observation group was treated with low molecular heparin calcium combined with rivaroxaban. Clinical efficacy, indexes of blood gas analysis and coagulation function before and after treatment, and incidence of adverse reactions were compared between two groups. Results The disease control rate(DCR)of the observation group was 85.71%, which was higher than 71.43% of the control group(P>0.05). After treatment, the arterial oxygen partial pressure ［p(O₂)］ and blood oxygen saturation(SpO₂)levels significantly increased in both groups(P<0.05), the arterial carbon dioxide partial pressure ［p(CO₂)］ level significantly decreased in both groups(P<0.05), and the p(O₂)and SpO₂ levels in the observation group were significantly higher than the control group(P<0.05), while the p(CO₂)level was significantly lower than the control - group(P<0.05). After treatment, the levels of fibrinogen(FIB)and D-dimer(D-D)significantly decreased in both groups(P<0.05), the values of thrombinogen time(PT)and activated partial thromboplastin time(APTT)significantly increased in both groups(P<0.05), and the levels of FIB and D-D in the observation group were significantly lower than the control group(P<0.05), while the values of PT and APTT were significantly higher than the control group(P<0.05). During treatment, the incidence of adverse reactions in the observation group was 9.52%, which was lower than 19.04% in the control group(P>0.05). Conclusion The efficacy of low-molecular heparin calcium combined with rivaroxaban is effective in the treatment of elderly patients with advanced lung cancer complicated with pulmonary embolism, which can improve the respiratory and coagulation functions of patients.