Steel pipe contour online measurement method

A steel pipe contour online measurement method comprises a first step of installing four laser displacement sensors capable of moving up and down synchronously at two sides, whose distance is greater than the diameter of a steel pipe, to an end of the steel pipe, dividing the laser displacement sensors into two groups by taking one laser displacement sensor at one side and one corresponding laser displacement sensor at the other side as a group; a second step of using the two groups of laser displacement sensors for respectively measuring two groups of contour data of the steel pipe; a third step of calculating an included angle between a connecting line of the laser displacement sensors in one group and a radial cross section of the steel pipe based on the two groups of contour data; and a fourth step of performing projection mapping of the above included angle so as to obtain contour data of the radial cross section of the steel pipe. The invention has the advantage of eliminating errors due to axis deviation of the steel pipe.