This study reports the effect of sulfuric acid concentration on chalcopyrite chemical leaching in very simple H2SO4 solution systems ranging from 23g/L to 30g/L, with 2.5% chalcopyrite concentrate at 30°C. Copper extraction from chalcopyrite increases with an increase in sulfuric acid concentration, e.g. 86%, 90% and 92% after 96 days at 23g/L, 25/L and 27g/L H2SO4 solution respectively. Sulfur element formed on the surface of chalcopyrite was very porous as the result of an electron probe microanalyzer (EPMA). Copper extraction, however, leveled out at 35% after 20 days when the sulfuric acid concentration was higher than 28g/L on 25g/L of chalcopyrite concentrate. Sulfur element was detected by X-ray analysis as only a leaching reaction product. The passivation may be caused by thick elemental surface formed on the surface of chalcopyrite.