[en] The addition of Zn into Cu matrix has been proved to enhance the Sn activity and accelerate the formation of a Nb₃Sn layer in internal tin-processed Nb₃Sn wires. However, in our samples, Ti is doped in Sn cores, and during the reaction, Ti was observed to accumulate between the inner and outer sub-elements of the 1980-Nb-core multi-filamentary brass matrix wires. With the addition of Mg into the brass matrix, Ti accumulation between the sub-elements was significantly suppressed, which promoted Ti incorporation into the Nb₃Sn layers. Meanwhile, the formed Nb₃Sn layers exhibited smaller grain sizes. Compared to the brass (Cu-12wt%Zn) matrix wires, an improvement of critical current density (J _c) was found in the Cu-12Zn-0.2Mg matrix wires due to the incorporation of Ti into the Nb₃Sn layer and the refinement of the Nb₃Sn grain size. The irreversibility field (B _irr) and maximum bulk pinning forces (F _p,max) were calculated from the Kramer plot by analyzing the J _c(B) curves. A small amount of Mg (0.2 wt%) doping into the Cu-12Zn matrix wires can increase the B _irr value by about 0.5 T and the F _p,max value by about 3 ∼ 4 GN m⁻³ after the wires were heat treated between 670 °C and 730 °C. The non-Cu J _c of the Cu-12Zn-0.2Mg matrix wires reaches the maximum value of 1533 A mm⁻² @12 T after heat treatment at 685 °C and decreases at higher temperatures. (paper)