The content of high Tc phase Bi₂Sr₂Ca₂Cu₃O_x in the sintered specimen increased remarkably when a small amount of powder of 2223 phase was added to the starting powder as seeds. The 2223 phase was of more than 90% when sintered at 860°C for 150h with 10 wt% of 2223 powder added. A small amount of impurity phases such as Ca2CuO3 was selectively dissolved in water. Powder of 2223 phase without other phases was obtained.