The purpose of this study was to investigate the three-dimensional displacement of the cantilever fixed partial denture (CFPD) under an oblique loading. One Beagle dog was used in this experiment. The CFPD, which used the second premolar and the first molar as abutments and the second molar as pontic, was made in vitro fresh mandible of the Beagle dog, and the digital laser speckle (DLS) technique was employed to measure the three-dimensional displacement of the CFPD under the oblique loading for the first time. We found that when an oblique loading was exerted on the pontic, the displacement of CFPD was the greatest, and the displacement of the abutment near the pontic was smaller than that of the pontic but greater than that of the abutment far from the pontic. We also found that when an oblique loading was exerted on the abutment, the displacement of the directly loaded abutment was greater than that of the other abutment and the pontic. Under the oblique loading, the displacement increased with increasing of load. The experiment demonstrated that it would be advisable for the clinicians to avoid oblique loading, especially the oblique loading of the pontic when using the CPDF. The DLS technique may be one kind of methods for measuring the three-dimensional displacements of the small and irregular objects.