Abstract: Elaborated here in the paper is the manufacturing process of Ф460 mm PQF hot-rolling mill+Ф720mm rotary expanding mill to produce large-sized，medium and light-wall P91 seamless steel pipes. Also analyzed arethe properties of the said P91 pipe. As a result it is identified that the chemical composition，the geometric dimensions and the mechanical properties of the pipe as made by the above mentioned process are in compliance withapplicable specification，and that its rupture strength is equivalent to that of the pipe as made with the conventionalahot-rolling process. The pipe is applicable to service in the hi-temperature/hi-pressure environment.