This study aimed to investigate the effect of hetrombopag combined with conventional treatment on immune function in patients with severe aplastic anemia (SAA). Patients were categorized into the control group (n = 50, receiving conventional treatment only) and experimental group (n = 50, receiving hetrombopag combined with conventional treatment). Before treatment and at weeks 18, 24, and 52 after treatment, the two groups were compared in routine blood test indicators, natural killer (NK) cell activity, and peripheral blood inflammatory factor levels. The overall remission rate and incidence of adverse events were also compared between the two groups. Outpatient or telephone follow-up was performed before treatment and at weeks 18, 24, and 52 after treatment to observe patients' immune function, treatment outcome, quality of life, and adverse events. Hemoglobin (Hb), and platelet count (PLT) (P < 0.05), and a rise in NK cell activity (P < 0.05). Interleukin (IL-10) levels were significantly higher, while IL-6 levels were significantly lower in the experimental group compared to the control group (P < 0.05). After receiving the treatment, all scores of SF-36 domains in both groups were higher than before treatment, particularly with higher scores in the experimental group (P < 0.05). Hetrombopag combined with conventional treatment improved the immune function and hematopoiesis of patients with SAA.