Owing to suffering the poor recovery of valuable metals and the massive loss of Co metal by the traditional pyrometallurgical technology processing low-nickel matte. Herein, a sulfate roasting followed by water leaching process was developed as an efficient technology for the simultaneous extraction of Ni, Cu, and Co from low-nickel matte in the presence of (NH4)2SO4 additive. The influence of roasting temperature, the dosage of ammonium sulfate, and roasting rules on the leaching efficiency of metals are conducted. Also, the characterizations of phase evolution are complemented with the theoretical analysis of thermodynamic calculation to reveal the mechanism of (NH4)2SO4 added sulfate roasting. The results demonstrate that the (NH4)2SO4 plays a critical role in reducing the reaction temperature and improving the metal selectivity, achieving higher extraction efficiency of Ni, Cu, and Co (90.12%, 81.82%, and 92.45%, respectively), while Fe is only 10.18%, thus, the high selectivity extraction can be achieved.