Effects of the fluctuation range of formation temperature on preparation and superconducting properties of the Bi(Pb)2223 phase have been investigated in detail. Our results show that knowledge about the temperature distribution and fluctuation in the muffle furnace is necessary for preparation of the Bi(Pb)2223 single-phase. Single-phase samples from Bi_0.17Pb_0.3Sr₂Ca₂Cu₃O_y were obtained by a solid-state reaction in air at 835±5C. The best superconducting property of the as-prepared samples shows a one-step transition of a.c. susceptibility withT _c=109 K. Using this optimum sintering temperature and keeping the temperature fluctuation less than 5C, we have prepared pure Bi(Pb)2223 single-phase samples with good reproducibility.