To explore the mechanisms by which HFBI fusions increase recombinant fusion protein accumulation in plants. The HFBI sequence from Trichoderma reesei was synthesized and two plant expression vectors for expression of green fluorescence protein (GFP) and GFP-HFBI were constructed. The vectors were inoculated in Nicotiana benthamiana plants through agroinfiltration, and the expression levels and mRNA accumulation levels of GFP in Nicotiana leaves were examined by Western blotting, ELISA and RT-PCR. The HFBI fusion tag significantly enhanced the accumulation of GFP in the leaves of N. benthamiana without causing toxic effects. Endoplasmic reticulum-targeted GFP-HFBI fusion induced the formation of spherical protein particles in the plant cells. HFBI fusions can increase the accumulation of its fusion partner in plants by forming stable protein particles, which probably shields the target protein from endogenous protease-induced degadation. HFBI fusion technology provides an alternative to improving recombinant p