The effect of DMSO and sodium butyrate on the production of recombinant hepatitis A virus (HAV) capsid protein VP1 was evaluated and optimized in the culture of stably transfected $Drosophila$ $melanogaster$ S2 cells using culture plates and spinner flasks. The effect of DMSO and sodium butyrate was also evaluated to improve the recombinant VP1 production in stably transfected $Drosophila$ S2 cells. A production level of 0.88 mg of recombinant VP1/liter was obtained in the culture-plate culture of stably transfected S2 cells at 6 days after induction with 0.5 mM $CuSO_4$. The supplements of 2% DMSO and 10 mM sodium butyrate at 4 days post-inoculation increased recombinant VP1 accumulation by 141 and 104%, respectively, resulting in 2.17 and 1.7 mg/liter of recombinant VP1 production. In spinner flasks, recombinant VP1 production reached maximum level at 9 days after induction with 0.5 mM $CuSO_4$, with approximately 4.96 mg/liter of recombinant VP1 production level. When 2% DMSO or 10 mM sodium butyrate was added at 5 days post-inoculation, the recombinant VP1 production was increased to 8.35 and 5.85 mg/liter, respectively. However, the synergistic effects of DMSO and sodium butyrate were not observed. These results indicate that DMSO and/or sodium butyrate can be successfully used to improve the recombinant HAV VP1 production in culture plates and spinner flasks.