Abstract: A machining method of a pipe welding type mixing faucet, which has a transverse connecting tube, two switch control valve seats, two screwed pipes, a discharge pipe coupling seat, a discharge pipe and a housing made of stainless steel. Reduced abutting ring surfaces are separately fabricated into the discharge hole and bottom port of two switch control valve seats as well as the discharge through-hole of the transverse connecting tube, allowing for abutting of the transverse connecting tube, screwed pipe and discharge pipe coupling seat. The mating points are welded securely. With these machining methods, the pipe welding type mixing faucet allows for water flow through a stainless steel structure, thus improving sanitary quality and safety of potable water.