Realgar as a kind of arsenic agent is currently used to treat APL in China. The effectiveness and low toxicity of realgar have been verified, lower than arsenic trioxide. Although the therapeutic efficacy of realgar is blocked severely by its poor insolubility in water. In our lab, we addressed this problem by obtaining realgar bioleaching solution (RBS) from microbiological leaching technique. To develop a tradition Chinese medicinal formula (TCMF) for clinical application realgar is usually used with other herbs. However, treated realgar with RBS has not been evaluated in TCMF contain realgar. In the present study we used NB4 to investigate the effects of novel Realgar-Indigo naturalis formula (FRBS) on cell proliferation and apoptosis. We used MTT assay to measure anti proliferative activity of FRBS. We further study the effects of FRBS on cell growth and apoptosis according flow cytometry, DNA fragmentation assay and Fluorescence microscopy and Western blot. The results revealed that FRBS significantly inhibited growth in a dose-dependent manner, and induced apoptosis in NB4 cells. NB4 cell inhibitory response to FRBS at 2μg ml-1 of arsenic concentration was twofold higher, dissimilar to RIF, and induced apoptosis more effectively. Further, a higher expression of caspase-3, caspase-9 and cytochrome C from increased from FRBS. RBS can substitute the traditional realgar powder in RIF in order to provide a novel and promising Realgar-Indigo naturalis formula to treat acute promyelocytic leukemia.