It is necessary to obtain the depth information of a cement clinker for distributing the cooling air in a grate cooler reasonably. Considering the high-temperature in the grate cooler, a mesh-candidate-based online 3D measurement method was proposed to reconstruct the the cement clinker. A binocular stereo system composed of two cameras with the optical axes intersected was used to capture the images of the cement clinker and a wavelet multi-resolution algorithm was adopted to improve the efficiency of the measurement system. If the confidence coefficient value is lower, a few candidates should be rematched using a larger or smaller windows according to the histogram, by which the measurement error caused by ambiguity could be reduced. Experiments indicate that the root-mean-square error of the system is 4.29 mm, which meets the requirement of the measurement precision. The measurement method shows its advantages in simplified implementation, high accuracy and low costs,and it can be stably applied to the production line of the grate cooler.