The invention relates to the technical field of petroleum transportation, in particular to a machining fixture for a petroleum conveying device. The machining fixture comprises a base; the top of thebase is fixedly connected with a clamping base; a pipe body is placed at the top of the clamping base; the side surface of the top of the support base is fixedly connected with a limiting baffle plate; the side surface of the top of the base is fixedly connected with a support plate through a support frame; the middle part of the support plate penetrates through and is fixedly connected with a pressure driving mechanism; the bottom of the pressure driving mechanism fixedly communicates with the end, far from the pipe body, of the limiting mechanism through an air guide pipe; the end, near thepipe body, of the limiting mechanism penetrates through the side surface of the limiting baffle plate; and a positioning mechanism is arranged at the top of the limiting baffle plate. The pressure driving mechanism presses the limiting mechanism; pressed high-pressure gas drives limiting sleeves to move to extrude and fix the pipe body; and the limiting sleeves on the two sides extrude and fix thepipe body at the same time, so that the fixing efficiency of the pipe body is improved.