A three-dimensional (3D) reconstruction measurement method based on depth candidates is proposed for online measurement of cement clinkers thickness.A line laser is projected from the top and stereo cameras are used to acquire images of clinker surface.Establishing the depth candidates on vertical plane in which the laser stripes looate in the world coordinate system,the depth is recovered according to intersection of the corresponding line on parallax image ofthe candidates and the laser stripe in the images.The experiment proves the validity,accuracy of the method and computing speed,and it can be applied to online 3D reconstruction of cement clinkers during transport.