The invention provides a supporting frame for machining a turbine high pressure outer cylinder back oblique pipe orifice through a boring machine facing head, and relates to a supporting frame for machining a turbine high pressure outer cylinder back oblique pipe orifice through a boring machine facing head, and aims to solve the problems that in the prior art, one side of a high pressure outer cylinder is cushioned up through a mat box so that a certain angle can be formed between the high pressure outer cylinder and a workbench, and the position and the height of the mat box should be adjusted repeatedly, and time and labor are wasted in the process. A first connecting lug assembly is fixedly connected with a base and the first connecting lug assembly is connected with a first rod through a first hinge pin in a rotating mode, a boss is fixedly connected with the other end of the first rod, two stop pieces are fixedly connected with the first rod and a gap is formed between the two stop pieces, a second connecting lug assembly is fixedly connected with the base, one end of a second rod is connected with the second connecting lug assembly through a second hinge pin in a rotating mode, both the first hinge pin and the second hinge pin are arranged parallel to the wide edges of a rectangular plate, a groove is formed in the other end of the second rod, and the groove is matched with the first rod which is arranged between the two stop pieces. The supporting frame for machining the turbine high pressure outer cylinder back oblique pipe orifice through the boring machine facing head is used for supporting the boring machine facing head so that the turbine high pressure outer cylinder back oblique pipe orifice can be machined.