The utility model discloses a fixing device for circular pipe measurement by a pitot tube. The device comprises two V-shaped brackets which are symmetrically connected together, are identical in size and structure and have an included angle of beta 1. The two V-shaped brackets are connected by a connector, one V-shaped bracket is provided with a positioning frame, the positioning frame is provided with a positioning hole allowing the pitot tube to pass through, and the connector is provided with a fixing hole coaxial with the positioning hole. Each V-shaped bracket is composed of two equal-length rods of which the included angle is beta 2. A diameter line of the cross section of a pipe can be determined through the double V-shaped brackets. The pitot tube is fixed on a diameter line of the cross section of a pipe to be measured through the fixing hole and the positioning hole. The pitot tube passes through the fixing hole and the positioning hole, then passes through a measurement hole of the pipe and enters the inside of the pipe to carry out flow speed measurement. During measurement carried out by using the fixing device, the pitot tube can move up and down so that the pitot tube can be adjusted to different positions to carry out measurement. The fixing device for circular pipe measurement by the pitot tube has the advantages of simple structure and convenient operation and is suitable for quickly fixing a measuring position of the pitot tube in a working site.