In order to overcome the difficulty of online measurement of the lar ge hot cylindrical forgings at very high temperature,a method combining the mobile devices with the binocular vision system is proposed in this paper.Firstly,the traditional binocular vision system is optimized,including usi ng the line green laser to mark clear stripes on forgings,using high-resolution cameras to get these stripes,settin g a 500nm filter on each camera for eliminating the thermal radiation′s influen ce and obtaining the forgings′ outlines synchronously at the same time,and placing the whole system on the rails instal led on a removable manual truck to expand the binocular vision system′s measurement range.Meanwhile another po int green laser is designed to get marking points in order to connect the measurement areas.And an electronic total station is used to track the left camera′s position to simplify the coordinate transformation.Then,the formu la for 3D data reconstruction of binocular vision system is corrected to adapt to the actual co nditions.The results show the error is under 1‰ when a Φ2×10m forging is measured in this way.This me thod is fast and accur ate,which can provide references for hot-state measurement of large forgings.